We could substitute u=x−1, but we would then still have the problem of the second term, 3, in the denominator. Instead, we take out a factor 3 from the denominator,
dx(x−1)2+3=dx331(x−1)2+1=31dx31(x−1)2+1
and move a factor 31 into the square (x−1)2,
31dx31(x−1)2+1=31dx3x−12+1.
Now, we substitute u=(x−1)3 and get rid of all the problems at once,