Share 'function equation and extrude component'

Hey guys,   I am trying to make a series of 9 circular floors that as they go up to the middle floor the diameter increases and from the middle to the top decreases to the original position.   I have used a function y= (1/10)*x²+(x+1) in order to have a concave down parabola. but the results don't seem to be the expected ones.   Also the extrude commant failed to receive data.   Can some have a l…