Exponential distribution?

Let Y= √X. If X follows an exponential distribution with mean theta, find E(Y)

cidyah2016-06-04T15:18:42Z

f(x) = λ e^(-xλ) , x > 0

λet y=sqrt(x)
x= y^2
dx/dy = 2y dy

g(y) = 2 λ y e^(-y^2 λ) , y > 0

E(y) =
http://www.wolframalpha.com/input/?i=integrate+2ky^2+e^%28-ky^2%29+dy,+y+%3D+0+to+infinity