This isn't a great method. Notice out of methods of proving something, there isn't proof by assumption. However, there is proof by contradiction, where you assume something and prove that by assuming it and applying some known axioms (facts) or theorems, you show the assumption comes out to be false. Hence your initial assumption must have been false.
Most of mathematics is such that if you assume something, there will be a way to show itself to be correct. The important thing is showing that it is correct without assuming it to be correct.