Want to know how? Let a=b. Multiply both sides by a. Now we have a^2=ab Subtract b^2 from both sides. Now we have a^2-b^2=ab-b^2 Factor. (a+b)(a-b)=b(a-b) Divide by (a-b). a+b=b But a=b, so b+b=b Simplify 2b=b Divide by b 2=1 You’re welcome. Edit: Congrats to LahDsai to finding the error. Yes, the proof technically divides by zero. Not sarcastic at all, nice job. Took me a little bit of my own time to find the error.