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The base of a solid is the region enclosed by the graphs of 
y=x^(2)-5x+7 and 
y=3, between 
x=1 and 
x=4.
Cross sections of the solid perpendicular to the 
x-axis are rectangles whose height is 
x.
Which one of the definite integrals gives the volume of the solid?
Choose 1 answer:
(A) 
int_(1)^(4)(x^(2)-5x+4)*xdx
(B) 
int_(1)^(4)(-x^(2)+5x-4)*xdx
(C) 
int_(1)^(4)(x^(2)-5x+4)^(2)dx
(D) 
piint_(1)^(4)(x^(2)-5x+4)^(2)dx

The base of a solid is the region enclosed by the graphs of y=x25x+7 y=x^{2}-5 x+7 and y=3 y=3 , between x=1 x=1 and x=4 x=4 .\newlineCross sections of the solid perpendicular to the x x -axis are rectangles whose height is x x .\newlineWhich one of the definite integrals gives the volume of the solid?\newlineChoose 11 answer:\newline(A) 14(x25x+4)xdx \int_{1}^{4}\left(x^{2}-5 x+4\right) \cdot x d x \newline(B) 14(x2+5x4)xdx \int_{1}^{4}\left(-x^{2}+5 x-4\right) \cdot x d x \newline(C) 14(x25x+4)2dx \int_{1}^{4}\left(x^{2}-5 x+4\right)^{2} d x \newline(D) π14(x25x+4)2dx \pi \int_{1}^{4}\left(x^{2}-5 x+4\right)^{2} d x

Full solution

Q. The base of a solid is the region enclosed by the graphs of y=x25x+7 y=x^{2}-5 x+7 and y=3 y=3 , between x=1 x=1 and x=4 x=4 .\newlineCross sections of the solid perpendicular to the x x -axis are rectangles whose height is x x .\newlineWhich one of the definite integrals gives the volume of the solid?\newlineChoose 11 answer:\newline(A) 14(x25x+4)xdx \int_{1}^{4}\left(x^{2}-5 x+4\right) \cdot x d x \newline(B) 14(x2+5x4)xdx \int_{1}^{4}\left(-x^{2}+5 x-4\right) \cdot x d x \newline(C) 14(x25x+4)2dx \int_{1}^{4}\left(x^{2}-5 x+4\right)^{2} d x \newline(D) π14(x25x+4)2dx \pi \int_{1}^{4}\left(x^{2}-5 x+4\right)^{2} d x
  1. Calculate length function: To find the volume of the solid, we need to integrate the area of the cross-sections along the xx-axis from x=1x=1 to x=4x=4. The area of each rectangular cross-section is given by the length times the height. The length of each rectangle is the difference between the two functions y=x25x+7y=x^2-5x+7 and y=3y=3, and the height is given as xx.
  2. Simplify length function: First, we calculate the length of the rectangle, which is the difference between the two y-values: y=3y=3 and y=x25x+7y=x^2-5x+7. This gives us the function for the length of the rectangle: 3(x25x+7)3 - (x^2-5x+7).
  3. Calculate area function: Simplify the function for the length of the rectangle: 3(x25x+7)=x2+5x43 - (x^2-5x+7) = -x^2+5x-4.
  4. Integrate area function: Now, we multiply the length of the rectangle by its height xx to get the area of the cross-section: A(x)=x(x2+5x4)=x3+5x24xA(x) = x(-x^2+5x-4) = -x^3+5x^2-4x.
  5. Verify integral choice: To find the volume of the solid, we integrate the area function A(x)A(x) from x=1x=1 to x=4x=4. This gives us the definite integral: V=14(x3+5x24x)dxV = \int_{1}^{4} (-x^3+5x^2-4x) \, dx.
  6. Verify integral choice: To find the volume of the solid, we integrate the area function A(x)A(x) from x=1x=1 to x=4x=4. This gives us the definite integral: V=14(x3+5x24x)dxV = \int_{1}^{4} (-x^3+5x^2-4x) \, dx.Looking at the answer choices, we see that the correct integral matches the one we derived: V=14(x3+5x24x)dxV = \int_{1}^{4} (-x^3+5x^2-4x) \, dx, which corresponds to choice (B).

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