Concept:Recognise the integrand as the derivative of xex+x1.Explanation:We are given: ∫(1+x−x1)ex+x1dx.First, note that dxd(x+x1)=1−x21.Now, observe that 1+x−x1=x(1−x21)+1.So, the integrand becomes:[x(1−x21)+1]ex+x1=xex+x1(1−x21)+ex+x1.This is exactly of the form xf′(x)+f(x), where f(x)=ex+x1.Using the standard result: ∫[xf′(x)+f(x)]dx=xf(x)+c, we get:∫(1+x−x1)ex+x1dx=xex+x1+c.Answer:B. xex+x1+c