If the equation x2+px+q=0 and x2+qx+p=0, have a common root, then p + q + 1 =
0
1
2
-1
Let α is the common root, so α2+pα+q=0
and α2+qα+p=0
⇒ (p - q) α + (q - p) = 0 ⇒ α=1
Put the value of α , p + q + 1 = 0
If every pair of the equations x2+px+qr=0 , x2+qx+rp=0 , x2+rx+pq=0 have a common root, then the sum of three common roots is