Спростіть вираз : (3m-4n)(3m+5n)-(4,5m-n)(2m+4n)

Question

Спростіть вираз : (3m-4n)(3m+5n)-(4,5m-n)(2m+4n)

Answer 1

9m^2+15mn-12mn-20n^2-(9m^2+18mn-2mn-4n^2)=9m^2+15MN-12MN-20n^2-9m^2-18MN+2MN+4N^2=-16n^2-13mn

Answer 2

9m^2+15mn-12mn-20n^2-9m^2-18mn+2mn+4n^2=-16n^2-13mn