Question

3) Factorise:x^2- 10x + 21
a) (2x + 9)(x - 2)
b) (x-7)(x-3)
c) (x + 3)(x + 7)
d) (2x - 9)(x + 2)​

Answer 1

Answer:

a)(2x+9)(x-2)

= 2x(x-2)+9(x-2)

=2x²-4x+9x-18

=2x²+5x-18

b)(x-7)(x-3)

=x(x-3)-7(x-3)

=x²-3x-7x+21

=x²-10x+21

c)(x+3)(x+7)

=x(x+7)+3(x+7)

=x²+7x+3x+21

=x²+10x+21

d)(2x-9)(x+2)

=2x(x+2)-9(x+2)

=2x²+4x-9x-18

=2x²-5x-18