4 a b 2 9 ab 2 July 8, 2019 16 32 64 128 Factorise 4 a b 2 9 ab 2 If a 2 b 2 9 and ab 4 4 9 * a 2 b 2 4 3 * ab A 2 b 2 4 c 2 9 ab bc 3 2 3ca 2 a b 4 c 9