Integrating x/2: Why is u-substitution not being used?

[bobsmith76]

Homework Statement

I don't understand why the x/2 is not being integrated. I would think one should use u substitution. u = x/2, du = x, but they're not doing that.

 

[abhinav111]

Actually the book referred has used this substitution and have finally put u=x/2 again as question is asked in form of x/2 and not in u.

 

[Char. Limit]

Actually, they DID, but they skipped a couple of steps (like explaining HOW they integrated). If you try a u-substitution, you'll get the same answer they did.