1=12=(-1)2=√1, yes? Are we all familiar with that? (What? You're not? Oh, go take a math class.)
Therefore:
√12=√(-1)2
=1  =-1 (since square roots always cancel out square powers)
Therefore 1=-1 and 2=0 (adding 1 to both sides).

So what's the problem? Well, the problem is: square roots do not cancel out square powers, although they certainly appear to. Ever heard of BODMAS or PEMDAS? Same thing, different acronym. Evaluate 12 or (-1)2 first, then find the root of the answer. It ends up coming out to 1 both times.

Also: ever heard of the modulus or piecewise function? It's defined as √x2 or |x|, and its graph looks like

          y
 \        |        /
  \       |       /
   \      |      /
    \     |     /
     \    |    /
      \   |   /
       \  |  /
        \ | /
         \|/
---------------------x
          |
          |

Note that y=x looks like:

         y
         |        /
         |       /
         |      /
         |     /
         |    /
         |   /
         |  /
         | /
         |/
---------------------x
        /|
       / |
      /  |
     /   |
    /    |

and nothing like our friend |x|.

God, I love proving stuff.