I am having another one, costing me some trouble
On what basis are you thinking that the posted "answer" is correct? Since there is a "d" variable in both the numerator and denominator of the left-hand side, it would appear that this is not completely simplified. (Were you in a more-advanced course, I would suspect that the answer represented a derivative.)
I would appreciate if someone could show me this ^^
Please reply showing your work so far, so the volunteers can help you find where you're going astray. Thank you!