Simplifying Expressions with Exponents- Fix for Issue #12976

 Fix for Issue #12976.
In the last hint, in the last stage before the final result,  made 1/k^2 = k^0-2 instead of just 1/k^2 = k^-2.

http://sandcastle.khanacademy.org/media/castles/orimilstein:patch-12/exercises/simplifying_expressions_with_exponents.html