Question

Factorize: m^2+4m-21​

Answer 1

Answer:

Comaring m

2

−4m−21 with the identity x

2

+(a+b)x+ab we not that ab = - 21, and a + b = - 4. So, (-7) + 3 = 4 and (-7)(3) = -21

Hence, m

2

−4m−21=m

2

−7m+3m−21

=m(m−7)+3(m−7)

=(m−7)(m+3)

Therefore m

2

−4m−21=(m−7)(m+3)