The limits of your integration should be y=0 and y=1.
You are using dy, not dx.
dy goes from y=0 to y=1.
The region bounded by the line y = 1 and the parabola x^2 = 4y
is revolved about the line y = 1.....
Take the rectangular elements of area parallel to the axis of revolution
I set :
radius = 1 - y
i need help
my answer seems to be undefined...