Question

factorise x-2y-x^2+4y^2

Answer 1

x-x^2-2y+4y^2
x(1-x)-2y(1-2y)
(x-2y)(1-x)(1-2h)

Answer 2

x-2y-x^2+4y^2

= 4y^2 - x^2 - 2y + x

= (2y)^2 - (x)^2 - 2y + x

= {(2y + x)(2y - x)} - (2y - x)

= (2y - x) {(2y + x) - 1}

= (2y - x)(2y + x - 1)