Bunuel
If \(p + q + r = 0\), where \(p ≠ q ≠ r\), then \(\frac{p^2}{2p^2 + qr} + \frac{q^2}{2q^2 + pr} + \frac{r^2}{2r^2 + pq}\) ?
(A) 0
(B) 1
(C) –1
(D) pqr
(E) p + q + r
Solution :
We can answer this question by plugging in values of p. q and r.
Let p = 1, q = 0 and r = -1 such that p + q + r = 0 and p ≠ q ≠ r
Then, we get :
\(\frac{p^2}{2p^2 + qr} + \frac{q^2}{2q^2 + pr} + \frac{r^2}{2r^2 + pq}\)
= \(\frac{1^2}{2 + 0} + 0 + \frac{(-1)^2}{2 + 0 }\)
= \(\frac{1}{2 }+ \frac{1}{2}\)
= \(1\)
Thus, we can eliminate options A, D and E as their value is each equal to be 0
Now, if p = 1, q = 2 and r = -3, then we have :
\(\frac{p^2}{2p^2 + qr} + \frac{q^2}{2q^2 + pr} + \frac{r^2}{2r^2 + pq}\)
= \(\frac{1^2}{2*(1)^2 - 6} + \frac{2^2}{2 * (2)^2 - 3} + \frac{(-3)^2}{2 * (-3)^2 + 2}\)
= \(\frac{1}{-4 }+ \frac{4}{5}\) + \(\frac{9}{20}\)
= \(1\)
Hence, the correct answer is
Option B.