Hello there. I recently installed the Physics Forums app and could not find the homework section in the categories so I beg your pardon from the following question. I am using Apostol's Calculus Volume 1 and have encountered a problem on page 72 number 21 (for those in possession of the text). The problem is as follows; Derive the following property of the integral as a consequence of theorems 1-45 and 1-46: The integral from b to a of f(c-x) dx is equal to the integral from (c-b) to (c-a) of f(x) dx. Pardon me, im using a tablet and the app does not seem to contain buttons for mathematical symbols.