Question

一个圆柱体的底面半径为2cm,高为12cm,将圆柱的底面半径增加acm,高不变,圆柱体的体积曾加多少?

Answer 1

【（a+2）^2-2^2]π×12

原式=x^2 -2x+1+y^2+4y-4-x^2 + y^2

=-2y^2+4y-3

原式=（a-b）^2 +4ab

=4+4

=8