If every pair from among the equation x2+px+qr=0,x2+qx+pr=0 and x2+rx+pq=0 has a common root, then the sum of the three common roots is
A
2(p+q+r)
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B
p+q+r
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C
−(p+q+r)
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D
pqr
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Solution
The correct option is Bp+q+r Let, a be the common root then satisfies the root in all the three equation we get, a2+ap+qr=0........(1)a2+aq+pr=0........(2)a2+ra+pq=0........(3) solving these, we get pa+qr=aq+rpa(p−q)=r(p−q)a=ralso,aq+rp=ar+pqa(q−r)=p(q−r)a=qsimilarly,a=q the sum of common roots=p+q+r