Question

Q30. Factorize x2 - 21x + 108
(a) (x - 12)(x - 9)
(b) (x + 12) (x - 9)
(c) (x - 12) (x + 8)
(d) (x + 12) (x + 8)​

Answer 1

Answer:

x² - 21x + 108

x² - 12x - 9x - 108

x ( x-12) - 9( x-12)

(x-12) (x-9)

(a) is the right answer

Answer 2

Answer:

x2-21x+108

=x2-(12+9)x+108

=x2-12x-9x+108

=x(x-12)-9(x-12)

=(x-12)(x-9).

Hence (a) is the correct answer.