Question

Factorise the following using the identity x2+(a+b)x+ab=(x+a)(x+b):
x2-xy-20y2

Answer 1

Answer:

(x-4y)(x+5)

Step-by-step explanation:

x^2-xy-20y^2

x^2+5xy-4xy-20y^2

x(x+5)-4y(x+5)

(x-4y)(x+5)