Find the mistake while proving

X2-x2=x2-x2                                       e.g. 52-52=52-52

Or, (x-x)= (x+x)(x-x)                                    Or, 5(5-5)=(5+5)(5-5)

Or, X=2x                                                 Or, 5=10

Or, 1=2                                                    Or, 1=2

Here, we have proved 1=2.If this is true whole mathematics is wrong. So, there is some mistake in the process. Find the mistake. Finding mistake: Here, we have cancelled(x-x)=0 on both sides i.e. we have written 0/0 as 1, that is blunder. Actually,0/0 is indeterminate form i.e. there  is no number of the form0/0. So, we cannot cancel 0 and 0 on both sides.