So the problem is ∫(6x+5)/(2x+1)dx. I know the proper way to solve this is to long divide these two expressions and then solve. However, I tried doing it with substitution. u = 2x+1 dx = du/2 I then reasoned that 3u + 2 = 6x+5 since 3(2x+1) + 2 = 6x+3+2 = 6x+5 so I substituted it on top. (1/2)∫(3u+2)/u du Solving this integral gives me (3/2)u + ln|u| + C which equals (6x+3)/2 + ln|2x+1| + C. However, Wolfram Alpha says the answer is 3x + ln|2x+1| + C. I don't understand what I did wrong or why I can't do what I did.