10 × 10
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Factorize 9x2 + y2 + z2 - 6xy + 2yz - 6zx. Hence find its value if x = 1, y = 2 and z = -1.
Asked by Topperlearning User | 4th Jun, 2014, 01:23: PM
Expert Answer:
9x2 + y2 + z2 - 6xy + 2yz - 6zx
= (3x)2 + y2 + z2 - 2 3x y + 2yz - 2 z 3x
= (3x - y - z)2
{Using (a-b-c)2=a2+b2+c2-2ab+2bc-2ca}
When x=1,y=2 and z=-1,
9x2 + y2 + z2 - 6xy + 2yz - 6zx
= (3x - y - z)2
= [3(1) - 2 - (-1)]2
= (3 - 2 + 1)2 = 22 = 4
10 × 10 = 100
Hope it was helpful,
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