## The problem

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Please explain secondlast to last step

## Answer provided by our tutors

We sugest you solve by intervals using the definition for absolute value

So, if both m,n > 0 or both m,n <0 the expresion becomes:

if m>0 and n < 0, or m <0 and n > 0 the expression becomes:

If m = 0 or n = 0 the expression is not defined because of the division by '0'.