Hello,

Note that

If a and b are integers, then there are a few possibilities :

3-ab=1 and a+b=5 (1)

3-ab=5 and a+b=1 (2)

3-ab=-1 and a+b=-5 (3)

3-ab=-5 and a+b=-1 (4)

From (1), we get ab=2, that is a=1 and b=2 for example. But a+b is not equal to 5. Impossible for integers.

From (2), we get ab=-2. We want a+b=1. --> a=-1 and b=2.

From (3), we get ab=4 --> a=-1 and b=-4

From (4), we get ab=8. Impossible for integers.