Y=(3x^2+7)^6
6 (3x^2+7)^5 d/dx [3x^2+7]
d/dx [3x^2]+d/dx [7]
6 (3x^2+7)^5 (d/dx [3x^2] +d/dx [7])
3 d/dx [x^2]
6 (3x^2+7)^5(3 d/dx [x^2]+d/dx [
7])
6 (3x^2+7)^5(3(2x)+d/dx [7])
6 (3x^2+7)^5(6x+d/dx [7])
6 (3x^2+7)^5(6x+0)
6 (3x^2+7)^5(6x)
36(3x^2+7)^5 x
36(3x^2+7)^5