question_answer

If \[A\text{ }=\text{ }7{{m}^{2}}+3mn-8{{n}^{2}},\text{ }B\text{ }=-4{{m}^{2}}+mn\]\[+4{{n}^{2}}\]and C = 3n2 - 4m2 - 4mn. Then find the value of A + B + C.

A) \[-{{m}^{2}}+mn-{{n}^{2}}\]

B) \[-{{m}^{2}}-mn-{{n}^{2}}\]

C) \[-{{m}^{2}}+{{n}^{2}}\]

D) \[-\left( {{m}^{2}}+{{n}^{2}} \right)\]

E) None of these