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Question
Factorise the following:
25x2 + 16y2 + 4z2 – 40xy + 16yz – 20xz
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Solution
25x2 + 16y2 + 4z2 – 40xy + 16yz – 20xz
= (–5x)2 + (4y)2 + (2z)2 + 2(–5x)(4y) + 2(4y)(2z) + 2(2z)(–5x) ...[Using identity, (a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ca]
= (–5x + 4y + 2z)2
= (–5x + 4y + 2z)(–5x + 4y + 2z)
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