Given : 9z2−x2+4xy−4y2
=9z2−(x2−4xy+4y2)
=9z2−[(x)2−2(x)(2y)+(2y)2]
Using the formula, (a−b)2=a2−2ab+b2
=9z2−(x−2y)2
=(3z)2−(x−2y)2
Using, a2−b2=(a+b)(a−b)
=[3z−(x−2y)][3z+(x−2y)]
=(3z−x+2y)(3z+x−2y)
=(−x+2y+3z)(x−2y+3z)
∴9z2−x2+4xy−4y2=(−x+2y+3z)(x−2y+3z).