I can't figure out how to solve this or why u wouldn't be equal to t^2

3. [0.5/8 Points] DETAILS MY NOTES 2 Use / g(u) du = 21 to answer the questions below. 0 4 (a) In this part, you will use the method of substitution to evaluate ] g(%) dt. 0 What substitution would be appropriate so that you can use the given information? u - X Use your substitution to rewrite the integral in terms of v only, and then evaluate it. [ T e 4 0T