Prove that 2=1.

let a=1, b=1.

So, a=b
multiply a for both sides, a*2 = ab --------[notes: * means power]
minus b*2 from both sides, a*2 - b*2 = ab - b*2
factorize, (a+b)(a-b) = b(a-b)
divide both sides by (a-b),
gives a+b = b
substitute a=1, b=1 into equation:
1+1=1
So, 2=1.

Got it?