This had been quite a story when I was in class 8. It took me quite a while to know where something was wrong. In case you wanted to refresh yourself with class 7-8 mathematics. Q. Prove 2=3. Sol. -6 = -6 => 4 - 10 = 9 - 15 => 4 - 10 + 25/4 = 9 - 15 + 25/4 => 2^2 - 2x2x(5/2) + (5/2)^2 = 3^2 - 2x3x(5/2) + (5/2)^2 => (2 - 5/2)^2 = (3 - 5/2)^2 => 2 - 5/2 = 3 - 5/2 => 2 = 3 //Proved// :-)