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Question
Factorise:
4x2 + 9y2 + 16z2 + 12xy – 24yz – 16xz
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Solution
It is known that,
(x + y + z)2 = x2 + y2 + z2 + 2xy + 2yz + 2zx
4x2 + 9y2 + 16z2 + 12xy – 24yz – 16xz
= (2x)2 + (3y)2 + (−4z)2 + 2(2x)(3y) + 2(3y)(−4z) + 2(−4z)(2x)
= (2x + 3y – 4z)2
= (2x + 3y – 4z)(2x + 3y – 4z)
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