Find the indefinite integral by making a change of variables. (x + 6 (x+6) VT-x dx Step 1 We are given the following indefinite integral and are told to make a change of variables to find the integral. (x+6)7 x dx 7-x It is generally best to use a substitution u = g(x) for the inner part of a composite function. In this case, there is a square root in the second factor. Therefore, we can set u to be the quantity under the square root. Find du. u = 7 x du = dx