Question

factorise
$x + xy + y + 1$

Answer 1

x + xy + y + 1

= x + 1 + xy + y

= (x + 1) + (xy + y)

= 1 (x +1) + y(x +1)

= (x + 1) ( 1+ y)

= (x + 1) (y + 1)