Calculus 2 Finding area and volume HW Problem?

Question

I need help with these two problems, PLease i cant figure them out

Find the area of the region that is bounded by f(x) = 1/2x and the parabola y^2 = 8 - x

Find the volume of solid generated by revolving the region bounded by the graphs of the equations y=x, y=3, and x=0 about the line y=4.

Answer 1

1) http://i299.photobucket.com/albums/mm286...

y=x/2 ==> x1=2y..........(1)

y^2=8-x ==> x2=8-y^2.......(2)

(1) and (2) intersect at x1=x2 ==>

2y=8-y^2

y^2+2y-8=0 ==> y=-4 or y=2

Area=∫[-4,2] (x2-x1)*dy=

∫[-4,2] (8-y^2-2y)*dy=

8y-y^3/3-y^2 [-4,2]=

16-8/3-4+32-64/3+16=60-72/3=36

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2) y1=x, y2=3, x=0

y1 and y2 intersect at x=3

V=π∫[0,3] [(4-y1)^2-(4-y2)^2]*dx=

π∫[0,3] [(4-x)^2-(4-3)^2]*dx=

π∫[0,3] (15-8x+x^2)*dx=

π(15x-4x^2+x^3/3) [0,3]=

π(45-36+9)=18π