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Question 76

The area (in sq. units) of the region described by $$\{(x, y) : y^2 \leq 2x, y \geq 4x - 1\}$$ is

y²≤2x and y≥4x-1. 

Intersection: y²=2x and y=4x-1

y²=2(y+1)/4=(y+1)/2

2y²=y+1. 2y²-y-1=0

y=1 or y=-1/2.

Area=$$\int_{-1/2}^1[(y+1)/4-y^2/2]dy$$=$$\int[(y+1)/4-y^2/2]dy.$$

=$$[y^2/8+y/4-y^3/6]_{-1/2}^1$$=(1/8+1/4-1/6)-(1/32-1/8+1/48).

=(3/24+6/24-4/24)-(3/96-12/96+2/96)=5/24-(-7/96)

=5/24+7/96=20/96+7/96=27/96=9/32.

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