Evaluate `int_(0)^(infty) x.e^(-x)dx`

Evaluate int_(0)^(infty) e^(-x)x^(3)dx .

" Evaluate "int_(0)^(t)x^(2)e^(-x)dx

The value of int_(0)^(infty)[2e^(-x)] dx (where ,[.] denotes the greatest integer function of x) is equal to S

Evaluate : int_(0)^(4)x.e ^(2x) dx

Evaluate int_(0)^(2)e^(x)dx

Evaluate int_(0)^(1)(e^(-x)dx)/(1+e^(x))

6.Evaluate int_(0)^(1)(e^(x)+x^(e))dx