# U substitution problem

∫3xdx/√(1-2x)

## The Attempt at a Solution

so i tried making u=3x which makes du=3dx but that substitution doesn't get rid of the x unde the square root. i tried u=1-2x and that gives du=-2dx and that doesn't get rid of the x on top. So i'm stuck and have no idea what to do here. Please help me out. Thanks!

Mark44
Mentor

∫3xdx/√(1-2x)

## The Attempt at a Solution

so i tried making u=3x which makes du=3dx but that substitution doesn't get rid of the x unde the square root. i tried u=1-2x and that gives du=-2dx and that doesn't get rid of the x on top. So i'm stuck and have no idea what to do here. Please help me out. Thanks!
Your second substitution will work if you replace x and dx with the corresponding values of u and du. Note that if u = 1 - 2x, then x = (1/2)(1 - u).