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questionďźAccording to the rule of combining like terms, we have 4x-2x+x=(4-2+1)x=3x; similarly, if we consider (a+b) as a whole, then 4(a+b)-2(a+b)+(a+b)=(4-2+1)(a+b)=3(a+b); this problem-solving method is called "whole thinking", and the application of whole thinking is extremely extensive in the simplification and evaluation of polynomials.**Try to Apply:**(1) Considering (a-b)^{2} as a whole, the result of combining 4(a-b)^{2}-6(a-b)^{2}+8(a-b)^{2} is ______;(2) Given x^{2}-2y=1, find the value of 2021x^{2}-4042y+1;**Explore Further:**(3) Given a-2b=2, 2b-c=-5, c-d=9, find the value of left(a-cright)+left(2b-dright)-left(2b-cright).
answerďźAlright, so I have these three problems to solve. Let me take them one by one. I remember the concept of "whole thinking" from the introduction. It's about treating a part of an expression as a single unit and combining like terms. That should help simplify things, right?Starting with problem (1): I need to combine (4(a - b)^2 - 6(a - b)^2 + 8(a - b)^2). Okay, so each term here has ((a - b)^2), which is the whole. So, similar to the examples given, I can factor that out and just combine the coefficients.Let me write that down:(4(a - b)^2 - 6(a - b)^2 + 8(a - b)^2)This is like (4x - 6x + 8x) where (x = (a - b)^2). So, combining the coefficients:(4 - 6 + 8 = (4 + 8) - 6 = 12 - 6 = 6). So, the result should be (6(a - b)^2). That seems straightforward.Moving on to problem (2): Given (x^2 - 2y = 1), find the value of (2021x^2 - 4042y + 1). Hmm, okay. So, I need to express the given expression in terms of the equation provided.Looking at the expression (2021x^2 - 4042y + 1), I notice that 2021 and 4042 are multiples. Let me see, 4042 divided by 2021 is 2. So, 4042y is 2 times 2021y. Wait, but in the given equation, we have (x^2 - 2y = 1). Maybe I can factor out 2021 from the first two terms.Let me try that:(2021x^2 - 4042y + 1 = 2021(x^2 - 2y) + 1)Yes, that works because 2021 times (x^2) is (2021x^2), and 2021 times (-2y) is (-4042y). So, now, from the given equation, (x^2 - 2y = 1), so substituting that in:(2021(1) + 1 = 2021 + 1 = 2022). So, the value is 2022. That makes sense.Now, problem (3): Given (a - 2b = 2), (2b - c = -5), and (c - d = 9), find the value of ((a - c) + (2b - d) - (2b - c)). Hmm, okay. Let me parse this step by step.First, let me write down what I need to find:((a - c) + (2b - d) - (2b - c))Let me simplify this expression before plugging in any values. Maybe I can combine like terms.Expanding the expression:(a - c + 2b - d - 2b + c)Wait, let's see:- The first term is (a - c).- The second term is (2b - d).- The third term is subtracted, so it's (-2b + c).So, combining all these:(a - c + 2b - d - 2b + c)Now, let's combine like terms:- (a) remains as is.- (-c + c = 0).- (2b - 2b = 0).- (-d) remains.So, the entire expression simplifies to (a - d). Interesting, so the value we need is (a - d).Now, how do I find (a - d) given the equations?Given:1. (a - 2b = 2)2. (2b - c = -5)3. (c - d = 9)I need to express (a - d) in terms of these equations. Let me see if I can link these equations together.From equation 1: (a = 2b + 2).From equation 2: (2b - c = -5), so (c = 2b + 5).From equation 3: (c - d = 9), so (d = c - 9). But since (c = 2b + 5), substituting that in, (d = (2b + 5) - 9 = 2b - 4).So now, I have expressions for (a) and (d) in terms of (b):- (a = 2b + 2)- (d = 2b - 4)Therefore, (a - d = (2b + 2) - (2b - 4))Let me compute that:(2b + 2 - 2b + 4 = (2b - 2b) + (2 + 4) = 0 + 6 = 6)So, (a - d = 6). Therefore, the value of the original expression is 6.Let me double-check my steps to make sure I didn't make any mistakes.Starting with the expression ((a - c) + (2b - d) - (2b - c)), I expanded it correctly:(a - c + 2b - d - 2b + c), which simplifies to (a - d). That seems right.Then, using the given equations:1. (a = 2b + 2)2. (c = 2b + 5)3. (d = c - 9 = 2b + 5 - 9 = 2b - 4)Thus, (a - d = (2b + 2) - (2b - 4) = 6). Yep, that checks out.So, all three problems solved. Let me recap:1. Combined the coefficients of ((a - b)^2) to get (6(a - b)^2).2. Factored out 2021 from the expression and substituted the given equation to get 2022.3. Simplified the expression to (a - d), then expressed (a) and (d) in terms of (b) and found the difference to be 6.Feeling confident about these answers.**Final Answer**(1) boxed{6(a - b)^2}(2) boxed{2022}(3) boxed{6}
questionďźGiven that the square root of the real number a+3 is pm 4, find the arithmetic square root and cubic root of the real number 5a-1.
answerďźOkay, so I have this math problem here. It says that the square root of the real number ( a + 3 ) is ( pm 4 ). I need to find the arithmetic square root and the cubic root of the real number ( 5a - 1 ). Hmm, let me try to figure this out step by step.First, the problem mentions that the square root of ( a + 3 ) is ( pm 4 ). Wait, square roots can be both positive and negative, right? So if the square root is ( pm 4 ), that means ( a + 3 ) must be equal to ( 4^2 ) or ( (-4)^2 ). But both of those are 16, right? So ( a + 3 = 16 ).Let me write that down:( sqrt{a + 3} = pm 4 )Squaring both sides, we get:( a + 3 = (pm 4)^2 )Which simplifies to:( a + 3 = 16 )So, solving for ( a ), subtract 3 from both sides:( a = 16 - 3 )( a = 13 )Okay, so ( a ) is 13. Now, the problem asks for the arithmetic square root and the cubic root of ( 5a - 1 ). Let me compute ( 5a - 1 ) first.Substituting ( a = 13 ):( 5a - 1 = 5 times 13 - 1 )Calculating that:( 5 times 13 = 65 )So,( 65 - 1 = 64 )Therefore, ( 5a - 1 = 64 ).Now, I need to find the arithmetic square root and the cubic root of 64.Starting with the arithmetic square root. The arithmetic square root is the non-negative root, so it's just the positive square root. So, what number squared gives 64?Well, 8 squared is 64 because ( 8 times 8 = 64 ). So, the arithmetic square root of 64 is 8.Next, the cubic root. The cubic root of a number is a value that, when multiplied by itself three times, gives the original number. So, what number cubed is 64?Let me think. 4 cubed is 64 because ( 4 times 4 times 4 = 64 ). So, the cubic root of 64 is 4.Wait, just to make sure I didn't make a mistake. Let me double-check my calculations.First, ( a + 3 = 16 ) leads to ( a = 13 ). Then, ( 5a - 1 = 5 times 13 - 1 = 65 - 1 = 64 ). That seems correct.Square root of 64 is 8 because ( 8^2 = 64 ). Cubic root of 64 is 4 because ( 4^3 = 64 ). Yep, that all adds up.So, I think I've got it. The arithmetic square root is 8, and the cubic root is 4.**Final Answer**The arithmetic square root of (5a - 1) is boxed{8} and the cubic root is boxed{4}.
questionďźGiven the parabola y^2 = 4x with focus F, and a line passing through F with an inclination angle of frac{pi}{4} intersects the parabola at points A and B, then |AB| = ______.
answerďźOkay, so I have this problem about a parabola and a line intersecting it. Let me try to figure it out step by step. The parabola is given by the equation ( y^2 = 4x ). I remember that for a parabola in the form ( y^2 = 4ax ), the focus is at ( (a, 0) ). Comparing that to our equation, ( 4a = 4 ), so ( a = 1 ). That means the focus ( F ) is at ( (1, 0) ).Now, the problem says a line passes through ( F ) with an inclination angle of ( frac{pi}{4} ). I think the inclination angle is the angle the line makes with the positive x-axis. So, if the angle is ( frac{pi}{4} ), that's 45 degrees. The slope of such a line should be ( tan(frac{pi}{4}) ), which is 1. So, the slope ( m ) is 1.Since the line passes through the focus ( F(1, 0) ) and has a slope of 1, I can write its equation using the point-slope form. The point-slope formula is ( y - y_1 = m(x - x_1) ). Plugging in the values, we get ( y - 0 = 1 cdot (x - 1) ), which simplifies to ( y = x - 1 ).So, the equation of the line is ( y = x - 1 ). Now, this line intersects the parabola ( y^2 = 4x ) at points ( A ) and ( B ). I need to find these points of intersection to determine the distance between ( A ) and ( B ).To find the points of intersection, I can substitute ( y = x - 1 ) into the equation of the parabola. Let's do that:Substitute ( y ) into ( y^2 = 4x ):( (x - 1)^2 = 4x )Let me expand the left side:( x^2 - 2x + 1 = 4x )Now, bring all terms to one side to form a quadratic equation:( x^2 - 2x + 1 - 4x = 0 )Simplify the like terms:( x^2 - 6x + 1 = 0 )So, the quadratic equation is ( x^2 - 6x + 1 = 0 ). I can solve this using the quadratic formula. The quadratic formula is ( x = frac{-b pm sqrt{b^2 - 4ac}}{2a} ), where ( a = 1 ), ( b = -6 ), and ( c = 1 ).Plugging in the values:( x = frac{-(-6) pm sqrt{(-6)^2 - 4 cdot 1 cdot 1}}{2 cdot 1} )Simplify:( x = frac{6 pm sqrt{36 - 4}}{2} )( x = frac{6 pm sqrt{32}}{2} )( sqrt{32} ) can be simplified to ( 4sqrt{2} ), so:( x = frac{6 pm 4sqrt{2}}{2} )Divide numerator terms by 2:( x = 3 pm 2sqrt{2} )So, the x-coordinates of points ( A ) and ( B ) are ( 3 + 2sqrt{2} ) and ( 3 - 2sqrt{2} ). Now, let's find the corresponding y-coordinates using the equation of the line ( y = x - 1 ).For ( x = 3 + 2sqrt{2} ):( y = (3 + 2sqrt{2}) - 1 = 2 + 2sqrt{2} )So, point ( A ) is ( (3 + 2sqrt{2}, 2 + 2sqrt{2}) ).For ( x = 3 - 2sqrt{2} ):( y = (3 - 2sqrt{2}) - 1 = 2 - 2sqrt{2} )So, point ( B ) is ( (3 - 2sqrt{2}, 2 - 2sqrt{2}) ).Now, I need to find the distance between points ( A ) and ( B ). The distance formula between two points ( (x_1, y_1) ) and ( (x_2, y_2) ) is ( sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} ).Let me compute the differences first:( x_2 - x_1 = (3 - 2sqrt{2}) - (3 + 2sqrt{2}) = -4sqrt{2} )( y_2 - y_1 = (2 - 2sqrt{2}) - (2 + 2sqrt{2}) = -4sqrt{2} )Now, square these differences:( (-4sqrt{2})^2 = 16 cdot 2 = 32 )So, both ( (x_2 - x_1)^2 ) and ( (y_2 - y_1)^2 ) are 32.Add them together:( 32 + 32 = 64 )Take the square root of 64:( sqrt{64} = 8 )So, the distance between points ( A ) and ( B ) is 8 units.Wait, let me double-check my calculations to make sure I didn't make any mistakes. The quadratic equation gave me x-values of ( 3 pm 2sqrt{2} ), which seems correct. Plugging back into the line equation, the y-values are ( 2 pm 2sqrt{2} ). Then, the differences in x and y are both ( -4sqrt{2} ), which when squared give 32 each. Adding them gives 64, and the square root of 64 is indeed 8. So, I think that's correct.Alternatively, I remember that for a parabola ( y^2 = 4ax ), the length of the focal chord (a chord passing through the focus) with a slope ( m ) can be found using the formula ( frac{4a(1 + m^2)}{m^2} ). Wait, is that right? Let me think.Actually, I think the formula for the length of the focal chord is ( frac{4a}{sin^2 theta} ), where ( theta ) is the angle the chord makes with the x-axis. Since here the angle is ( frac{pi}{4} ), ( sin frac{pi}{4} = frac{sqrt{2}}{2} ), so ( sin^2 frac{pi}{4} = frac{1}{2} ). Then, the length would be ( frac{4a}{1/2} = 8a ). Since ( a = 1 ), the length is 8. That matches my earlier result. So, that's a good confirmation.Therefore, I can be confident that the distance ( |AB| ) is 8.**Final Answer**The length of segment ( AB ) is boxed{8}.
questionďźTapanga and Corey have 66 candies together. However, Tapanga has 8 more candies than Corey. How many candies does Corey have?
answerďźFirst, I'll define variables to represent the number of candies each person has. Let ( C ) be the number of candies Corey has. Since Tapanga has 8 more candies than Corey, Tapanga has ( C + 8 ) candies.Next, I'll set up an equation based on the total number of candies they have together. The sum of Corey's and Tapanga's candies is 66, so:[C + (C + 8) = 66]Simplifying the equation:[2C + 8 = 66]Subtracting 8 from both sides:[2C = 58]Finally, dividing both sides by 2:[C = 29]Therefore, Corey has 29 candies.
questionďźGiven the lines l_1: 4x-3y+16=0 and l_2: x=-1, on the parabola y^2=4x, a moving point P has a distance d_1 to the line l_1 and a distance d_2 to the line l_2. Find the minimum value of d_1+d_2.
answerďźOkay, so I have this problem here where I need to find the minimum value of the sum of two distances, dâ and dâ, from a moving point P on the parabola y² = 4x to two given lines, lâ and lâ. The lines are lâ: 4x - 3y + 16 = 0 and lâ: x = -1. First, I should recall the formula for the distance from a point to a line. The distance from a point (xâ, yâ) to the line ax + by + c = 0 is given by |axâ + byâ + c| / sqrt(a² + b²). So, I can use this formula to express both dâ and dâ in terms of the coordinates of point P.Since P is on the parabola y² = 4x, I can parametrize P using the standard parametric equations for a parabola. For y² = 4x, the parametric equations are x = at² and y = 2at, where a is the focal length. Comparing with y² = 4x, we have 4a = 4, so a = 1. Therefore, the parametric coordinates of P can be written as (t², 2t). This will make it easier to express dâ and dâ in terms of a single variable t.So, let me write down the coordinates of P as (t², 2t). Now, let's compute dâ, the distance from P to lâ: 4x - 3y + 16 = 0.Using the distance formula:dâ = |4*t² - 3*(2t) + 16| / sqrt(4² + (-3)²) = |4t² - 6t + 16| / 5.Similarly, dâ is the distance from P to lâ: x = -1. Since lâ is a vertical line, the distance from P = (t², 2t) to lâ is simply the horizontal distance between x = t² and x = -1. So, dâ = |t² - (-1)| = |t² + 1|. Since t² is always non-negative, t² + 1 is always positive, so we can drop the absolute value: dâ = t² + 1.Therefore, the total distance we need to minimize is dâ + dâ = (|4t² - 6t + 16| / 5) + (t² + 1). Wait a second, the numerator in dâ is 4t² - 6t + 16. Let me check if this quadratic ever becomes negative. The quadratic 4t² - 6t + 16 has a discriminant D = (-6)² - 4*4*16 = 36 - 256 = -220, which is negative. That means the quadratic never crosses zero and is always positive because the coefficient of t² is positive. So, |4t² - 6t + 16| is just 4t² - 6t + 16. Therefore, dâ simplifies to (4t² - 6t + 16)/5.So, now, the expression to minimize is:dâ + dâ = (4t² - 6t + 16)/5 + t² + 1.Let me combine these terms. First, let's write t² as 5t²/5 to have a common denominator:(4t² - 6t + 16)/5 + (5t²)/5 + 1.Combine the terms:(4t² - 6t + 16 + 5t²)/5 + 1 = (9t² - 6t + 16)/5 + 1.Now, 1 can be written as 5/5, so:(9t² - 6t + 16 + 5)/5 = (9t² - 6t + 21)/5.Therefore, the expression simplifies to (9t² - 6t + 21)/5. So, we need to find the minimum value of this quadratic function in terms of t.Since this is a quadratic function in t, and the coefficient of t² is positive (9/5), the function opens upwards, so its minimum occurs at the vertex.The vertex of a quadratic function at² + bt + c is at t = -b/(2a). Here, a = 9/5, b = -6/5.Wait, hold on. Let me write the function as f(t) = (9t² - 6t + 21)/5. So, f(t) = (9/5)t² - (6/5)t + 21/5.So, in standard form, a = 9/5, b = -6/5, c = 21/5.Therefore, the vertex is at t = -b/(2a) = -(-6/5)/(2*(9/5)) = (6/5)/(18/5) = (6/5)*(5/18) = 6/18 = 1/3.So, the minimum occurs at t = 1/3.Now, let's compute f(1/3):f(1/3) = (9*(1/3)^2 - 6*(1/3) + 21)/5.Compute each term:9*(1/3)^2 = 9*(1/9) = 1.-6*(1/3) = -2.So, 1 - 2 + 21 = 20.Therefore, f(1/3) = 20/5 = 4.So, the minimum value of dâ + dâ is 4.Wait, hold on. Let me double-check my calculations because 9*(1/3)^2 is 1, -6*(1/3) is -2, and 21 is 21. So, 1 - 2 + 21 is indeed 20, and 20/5 is 4. So, that seems correct.But just to be thorough, let me verify if I correctly transformed the expression.We had dâ = (4t² - 6t + 16)/5 and dâ = t² + 1.So, dâ + dâ = (4t² - 6t + 16)/5 + t² + 1.Expressed as:(4t² - 6t + 16)/5 + (5t²)/5 + 5/5 = (4t² - 6t + 16 + 5t² + 5)/5 = (9t² - 6t + 21)/5.Yes, that's correct.So, the quadratic is (9t² - 6t + 21)/5, which we found the minimum at t = 1/3, giving 4.Therefore, the minimum value of dâ + dâ is 4.But wait, let me think again. Is there another way to approach this problem? Maybe using reflection properties of parabolas?I remember that for a parabola, the definition is the set of points equidistant from the focus and the directrix. The given parabola is y² = 4x, which has its focus at (1, 0) and directrix at x = -1, which is exactly the line lâ: x = -1.So, in this case, dâ is the distance from P to the directrix, which is equal to the distance from P to the focus (1, 0). So, dâ = distance from P to (1, 0).Therefore, dâ + dâ is equal to dâ + distance from P to (1, 0). So, we can rephrase the problem as finding the minimum of dâ + distance from P to (1, 0), where P is on the parabola y² = 4x.But dâ is the distance from P to the line lâ: 4x - 3y + 16 = 0. So, we need to minimize the sum of the distance from P to lâ and the distance from P to the focus (1, 0).Hmm, is there a geometric interpretation here? Maybe using reflection properties or something?Alternatively, perhaps using calculus, as I did before, is the straightforward way. But since I got an answer of 4, I should verify if that's correct.Wait, let me compute dâ + dâ at t = 1/3.So, P is (t², 2t) = ((1/3)^2, 2*(1/3)) = (1/9, 2/3).Compute dâ: distance from (1/9, 2/3) to lâ: 4x - 3y + 16 = 0.Using the distance formula:|4*(1/9) - 3*(2/3) + 16| / 5 = |4/9 - 2 + 16| / 5.Compute numerator:4/9 - 2 + 16 = 4/9 + 14 = (4 + 126)/9 = 130/9.So, |130/9| /5 = (130/9)/5 = 26/9 â 2.888...Compute dâ: distance from (1/9, 2/3) to x = -1 is |1/9 - (-1)| = |1/9 + 1| = 10/9 â 1.111...So, dâ + dâ = 26/9 + 10/9 = 36/9 = 4. So, that's correct.Therefore, the minimum value is indeed 4.Alternatively, if I think about reflecting the focus over the line lâ and then finding the distance from the reflection to the directrix or something, but that might complicate things.But since the calculus approach worked out and the verification shows that at t = 1/3, the sum is 4, which is the minimum, I think that's solid.Therefore, the minimum value of dâ + dâ is 4.**Final Answer**The minimum value of (d_1 + d_2) is boxed{4}.
questionďźA mixture of 30 liters of paint is 25% red tint, 30% yellowtint and 45% water. Five liters of yellow tint are added tothe original mixture. What is the percent of yellow tintin the new mixture?mathrm{(A)} 25 qquad mathrm{(B)} 35 qquad mathrm{(C)} 40 qquad mathrm{(D)} 45 qquad mathrm{(E)} 50
answerďźFirst, I need to determine the initial amounts of each component in the 30-liter paint mixture. The mixture is 25% red tint, 30% yellow tint, and 45% water.Calculating the amount of red tint:25% of 30 liters is 0.25 * 30 = 7.5 liters.Calculating the amount of yellow tint:30% of 30 liters is 0.30 * 30 = 9 liters.Calculating the amount of water:45% of 30 liters is 0.45 * 30 = 13.5 liters.Next, 5 liters of yellow tint are added to the original mixture. This increases the total amount of yellow tint to:9 liters + 5 liters = 14 liters.The total volume of the new mixture becomes:30 liters + 5 liters = 35 liters.Finally, to find the percentage of yellow tint in the new mixture, I divide the amount of yellow tint by the total volume and multiply by 100:(14 liters / 35 liters) * 100 = 40%.