The base of a solid is the region enclosed by the graphs of y=x2−5x+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) ∫14(x2−5x+4)⋅xdx(B) ∫14(−x2+5x−4)⋅xdx(C) ∫14(x2−5x+4)2dx(D) π∫14(x2−5x+4)2dx
Q. The base of a solid is the region enclosed by the graphs of y=x2−5x+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) ∫14(x2−5x+4)⋅xdx(B) ∫14(−x2+5x−4)⋅xdx(C) ∫14(x2−5x+4)2dx(D) π∫14(x2−5x+4)2dx
Calculate length function: To find the volume of the solid, we need to integrate the area of the cross-sections along the x-axis from x=1 to x=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=x2−5x+7 and y=3, and the height is given as x.
Simplify length function: First, we calculate the length of the rectangle, which is the difference between the two y-values: y=3 and y=x2−5x+7. This gives us the function for the length of the rectangle: 3−(x2−5x+7).
Calculate area function: Simplify the function for the length of the rectangle: 3−(x2−5x+7)=−x2+5x−4.
Integrate area function: Now, we multiply the length of the rectangle by its height x to get the area of the cross-section: A(x)=x(−x2+5x−4)=−x3+5x2−4x.
Verify integral choice: To find the volume of the solid, we integrate the area function A(x) from x=1 to x=4. This gives us the definite integral: V=∫14(−x3+5x2−4x)dx.
Verify integral choice: To find the volume of the solid, we integrate the area function A(x) from x=1 to x=4. This gives us the definite integral: V=∫14(−x3+5x2−4x)dx.Looking at the answer choices, we see that the correct integral matches the one we derived: V=∫14(−x3+5x2−4x)dx, which corresponds to choice (B).
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