27x3+y3+z3−9xyz=(3x)3+y3+z3−3(3x)×y×z
=(3x+y+z)((3x)2+y2+z2−(3x)y−y×z−z×(3x))
=(3x+y+z)(9x2+y2+z2−3xy−yz−3zx)
Factorise 27x3+y3+z3-9xyz
Factorise: 27x3+y3+z3−9xyz