3xdx/√(4+x)

need help!!!!

let u = 4+x

du = dx
x = u-4

3x/√(4+x) dx
= 3(u-4)/√u du
= (3u-12)/√u du
= 3u^(1/2) - 12u^(-1/2) du

Now it's just easy power rule stuff.