Factorise: 27x3+y3+z3−9xyz
It is known that, a3+b3+c3−3abc=(a+b+c)(a2+b2+c2−ab−bc−ac)
∴27x3+y3+z3−9xyz=(3x)3+(y)3+(z)3−3(3x)(y)(z)
=(3x+y+z)[(3x)2+(y)2+(z)2−(3x)(y)−(y)(z)−(3x)(z)]
=(3x+y+z)[9x2+y2+z2−3xy−yz−3xz]
Hence, 27x3+y3+z3−9xyz=(3x+y+z)[9x2+y2+z2−3xy−yz−3xz]