Question

factorisation plz help

Answer 1

$1 + x + y - z + xy - yz - zx - xyz \\ = 1 + x + y + xy - z - zx - yz - xyz \\ = (1 + x) + y(1 + x) - z(1 + x) - yz( 1+ x) \\ = (1 + x)(1 + y - z - yz) \\ = (1 + x)[(1 + y) - z(1 + y)]\\ = (1 + x)(1 + y)(1 - z)$