integral 3(-3+4x)^5 dx

u = -3 + 4x
du = 4 dx
dx = 1/4 du

∫3(-3 + 4x)^5 dx
= 3 ∫u^5 . 1/4 du
= 3/4 ∫ u^5 du
= 3/4 . 1/(5+1) u^(5+1) + C
= 3/24 (-3 + 4x)^6 + C
= 1/8 (-3 + 4x)^6 + C