计算不定积分∫(2x+3)^3dx
∫(2x+3)^3dx
= 1/2 * ∫(2x+3)^3d(2x+3)
= 1/2 * 1/4 * (2x+3)^4 + C
= 1/8 * (2x+3)^4 + C