Question

factorise m²+17m-84​

Answer 1

Answer:

${m}^{2} + 17m - 84 \\ = {m}^{2} + (21 - 4)m - 84 \\ = {m}^{2} + 21m - 4m - 84 \\ = m(m + 21) - 4(m + 21) \\ = (m - 4)(m + 21) \\ \\ m - 4 = 0 \\ m = 4 \\ \\ m + 21 = 0 \\ m = - 21$