Factorise the following:
(i) 9 (i) Given that: 9x2 + 4y2 + 16z2 + 12xy – 16yz – 24zx =(3x2 + (2y)2 + (−4z)2 + 2(3x)(2y) + 2(2y)(−4z) + 2(−4z)(3x) = (3x + 2y – 4z)2 [∵ a2 + b2 + c2 + 2ab + 2bc + 2ca) = (a + b + c)2] = (3x + y– 4z) (3x + 2y – 4z) (ii). Given that: 25