1. Find the centroids of the solids formed by rotating completely about the x-axis the plane regions defined by the following inequalities: (a) y^2 < 9x, y>0, x<1 (b) xy<4, y>0, 1<x<2 2. I used the equation for solids of revolution: Integral from a to b of (x[f(x)]^2.dx) / Integral from a to b [f(x)^2].dx 3. I drew the graph and found the region enclosed as per their requirement. For a, I got the function in terms of y so y=3 sqrt (x) then I plugged it into the equation provided in 2. I took the bounds as x=0 and x=1 for the integration but I don't think this is the way to do it for inequalities.