Answer:
[tex]\boxed{-7}[/tex]
Step-by-step explanation:
[tex]\sf (m- n)(n+ m)[/tex]
[tex]\sf m=3[/tex]
[tex]\sf n=4[/tex]
___________________
[tex]\sf \left(3-4\right)\left(4+3\right)[/tex]
Follow PEMDAS operations:
[tex]\sf \left(3-4\right)[/tex]
[tex]\sf =-1[/tex]
[tex]\sf \left(4+3\right)[/tex]
[tex]\sf =7[/tex]
[tex]-1\times \:7[/tex]
[tex]\sf =-7[/tex]
