2=1

Question

How can 2 = 1 be true?

Answer

Assume that a = b 

1.) a = b; assumption 
2.) a*a = a*b; multiply both sides by "a" 
3.) a^2-b^2 = a*b - b^2; subtract "b^2" from both sides 
4.) (a+b)*(a-b) = b*(a-b); factor 
5.) a+b = b; divide both sides by "(a-b)" 
6.) b+b = b; substitute "b" for "a" since "a=b" (assumption) 
7.) 2b = b; simplify 
8.) 2 = 1; divide both sides by b