integral (3x + 1) pangkat 6 DX

int (3x + 1)^6 dx
u = 3x + 1 -->> du = 3 dx
dx = (1/3) du
= int (1/3)u^6 du
= (1/3)(1/7)u^7 + c
= (1/21)(3x + 1)^7 + c