Question: prove 2 is equal to 1?
Answer: 1) a = b 1) Given.
2) a2 = ab 2) Multiply both sides by a.
3) a2-b2 = ab-b2 3) Subtract b2 from both sides.
4) (a+b)(a-b) = b(a-b) 4) Factor both sides.
5) (a+b) = b 5) Divide both sides by (a-b)
6) a+a = a 6) Substitute a for b.
7) 2a = a 7) Addition.
8) 2 = 1 8) Divide both sides by a.