Question

Why does the + 18 in step 2 become -18 in the working out below. Please explain in detail and this formula is calculating the first derivative of a function.

Answer 1

Explanation:

18/x is the same as 18•x-¹

derivative of ax^n=n•ax^n-1

derivative of 18•x-¹= -1•18•x-²

= -18x-² which is the same as -18/x²

hence 2-18/x²