Question

Допоможіть будь ласка,даю 50 балів!!!

Answer 1

${7m}^{2} + 5mn - {n}^{2} + ( { - 6m}^{2} ) + 2mn + {3n}^{2} + {m }^{2} + {c}^{2} = {7m}^{2} + 5mn - {n}^{2} - 12 {m}^{3}n + {3n}^{2} + {m }^{2} + {c}^{2} = 8 {m}^{2} + 5mn - 12 {m}^{3} n$