Question

and then 2+3=1+3 ,4=5 , 2+2=5.

please spot the mistake.

Answer 1

In step 5
You cancelled (a-b) from both sides which isn't allowed as a=b
Hence a-b is 0
And if you cancel 0 from both the sides, that means you are dividing 0 by 0 which is actually an indeterminate form.
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