My only concern is that the answer to a problem is not what is boxed but rather what comes after an equal sign.
The reason that your left hand side answer is correct is because the very top line (the integral you want to solve) EQUALS all the lines below that top line, especially the last line. The issue I have is nowhere did you state that the top line equals the bottom line. Please use equal signs. As a grader all I ever did was verify if one line equaled the next line and if there was no equal signs...let's just say that my students were not happy.