rotation of a bounded area question i can't solve

Write the integral in one variable to find the volume of the solid obtained by rotating the first-quadrant region bounded by y = 0.5x^2 and y = x about the line x = 5.

Question

rotation of a bounded area question i can't solve 

Write the integral in one variable to find the volume of the solid obtained by rotating the first-quadrant region bounded by y = 0.5x^2 and y = x about the line x = 5.

anonymous · Answer

my trouble is mainly with the fact that the rotation is done around x=5 and not the x axis

anonymous · Answer

im sure something changes but not sure what

anonymous · Answer

Do you prefer the washer or shell method?

anonymous · Answer

well i don't know the shell method so washer i suppose

anonymous · Answer

Observe that the dimensions of the washer that you'll be interested in (i.e. radius) will have to be written in terms of $y$.

Let's draw the region first:
|dw:1439519332453:dw|