Greetings , Im taking an online course on mathematical thinking, and this question has me stumped. r is irrational: Show that r+3 is irrational Show that 5r is irrational Show that the square root of r is irrational. Im sorry if i posted this in the wrong forum, but im not sure which category these questions fall under. I seriously dont even know where to start. Btw these questions are under the proofs section of the course.