用它分别求以下5个函数的定积分：

∫ab (1+x)dx , ∫ab (2x+3)dx , ∫ab (ex+1)dx , ∫ab (1+x)2dx ,

∫ab x3dx 。其中，a,b为积分上下限，数值待定。-Use it to find the following five functions, respectively, the definite integral: ∫ ab (1+ x) dx, ∫ ab (2x+3) dx, ∫ ab (ex+1) dx, ∫ ab (1+ x) 2dx, ∫ ab x3dx. One, a, b for the limits of integration, the value to be determined.