Answer:
[tex]\bf -m^2n^2+4m ^4-3n ^4[/tex]
Step-by-step explanation:
[tex]\bf -4m^2(n^2-m^2)+3n^2(m^2-n^2)[/tex]
Expand.
[tex]\bf -4m^2n^2+4m^4+3n^2m^2-3n ^4[/tex]
Collect like terms.
[tex]\bf (-4m ^2n^ 2+3m^2n^ 2)+4m ^4-3n^4[/tex]
[tex]\bf -m^2n^2+4m ^4-3n ^4[/tex]
