If (x + y + z) = 23 and x2 + y+ z= 179, then find the value of (xy + yz + zx).

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SSC Selection Post 2024 (Higher Secondary Level) Official Paper (Held On: 25 Jun, 2024 Shift 4)
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  1. 280
  2. 225
  3. 175
  4. 350

Answer (Detailed Solution Below)

Option 3 : 175
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Detailed Solution

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Given:

If (x + y + z) = 23 and x2 + y2 + z2 = 179, then find the value of (xy + yz + zx).

Formula used:

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

Calculation:

(x + y + z)2 = 232 = 529

x2 + y2 + z2 = 179

So, 529 = 179 + 2(xy + yz + zx)

⇒ 529 - 179 = 2(xy + yz + zx)

⇒ 350 = 2(xy + yz + zx)

⇒ 350/2 = xy + yz + zx

⇒ xy + yz + zx = 175

∴ The correct answer is option (3).

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