I'm sure there must be some explanation to why these kind of things appear.. firstly, consider a=b ab=b^{2} a^{2}-ab=a^{2}-b^{2} a(a-b)=(a+b)(a-b) a=a+b since a=b, b=b+b 1=2 !?? then this one- (100-100)/(100-100) =[(10+10)(10-10)/10(10-10)] =2 Anything has gone wrong?
Since a = b, then a - b = 0. To get to the line above, you divided by zero, which is never allowed. Here you cancelled (10 - 10)/(10 - 10), which is 0/0. You can't do that.