Question

Factorise by quadratic trinomials :- 1) x² + 10xy + 21y² 2) a² - ab - 20b²
3) 6 - 2x² - x
4) 14a² + 11ab - 15b²​

Answer 1

Answer:

A1)x²+10xy+21y²

= x²+3xy+7xy+21y²

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

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

A2)a²-ab-20b²

=a²-5ab+4ab-20b²

=a(a-5b)+4b(a-5b)

=(a+4b)(a-5b)

A3)6-2x²-x

( -2x²-x+6)×-1

= 2x²+x-6=

=2x²+4x-3x-6

=2x(x+2)-3(x+2)

=(2x-3)(x+2)

A4)14a²+11ab-15b²

=14a²+21ab-10ab-15b²

=7a(2a+3b)-5b(2a+3b)

=(7a-5b)(2a+3b)

Answer 2

I don't know the answer