Q1 of 59 Page 7

Expand the following

(x – 2y – 4z)2

(x – 2y – 4z)2


Here the identity used is


(x + y + z) 2 = x2 + y2 + z2 + 2xy + 2yz + 2zx


∴ (x – 2y – 4z) 2


= x2 + (– 2y)2 + (– 4z)2 + 2(x)(– 2y) + 2(– 2y)(– 4z) + 2 (– 4z)(x)


= x2 + 4y2 + 16z2 – 4xy + 16yz – 8yz


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