Which substitution is best for ∫11+xdx\int \frac{1}{1 + \sqrt{x}} dx∫1+x1dx?
u=1+xu = 1 + \sqrt{x}u=1+x
x=tan(θ)x = \tan(\theta)x=tan(θ)
u=x2u = x^2u=x2
u=xu = \sqrt{x}u=x