Start with the following simple equation: a=b (step 1) Multiply both sides by b: ab=b2 (step 2) Subtract a2 from both sides and factorize: ab−a2=b2−a2 (step 3) a(b−a)=(b+a)(b−a) (step 4) Simplify and add 1 to both sides: a=b+a (step 5) a+1=b+a+1 Now since a=b (the starting point of this proof), we can write this as: a+1=2a+1 And in the case where a=1, we have: 1+1=2+1 So, therefore, 1+1=3