If P2 + Q2 + R2 = 82 and Pq + Qr + Pr = 18; Find P + Q + R.

If p² + q² + r² = 82 and pq + qr + pr = 18; find p + q + r.

Sum

(p + q + r)²
= p² + q² + r²+ 2pq + 2qr + 2pr
= 8² + 2(18)
= 64 + 36
= 100
⇒ p + q + r
= `sqrt(100)`
= ± 10.

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Chapter 4 Expansions
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