If (x + y + z) = 23 and x2 + y2 + z2 = 179, then find the value of (xy + yz + zx).
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Correct answer: C
Explanation
The correct answer is Option 3 i.e. 175.
(x + y + z)2 = x2 + y2 + z2 + 2(xy + yz + zx)
⇒ 232 = 179 + 2(xy + yz + zx)
⇒ 529 - 179 = 2(xy + yz + zx)
⇒ 2(xy + yz + zx) = 350
⇒ xy + yz + zx = 175