a=b => a*b = b*b [ b গুণ করে ] => a*b - a*a= b*b - a*a [ a*a বিয়োগ করে ] => a (b-a) = (b+a) (b-a) => a = b + a [ (a -b) ভাগ করে ] => a = a + a => 1.a =2.a [যেহেতু a=b ] => 1 = 2