19 IfX2 - ax - 6 = 0 and x2 + ax - 2 = 0 have one common root, then a can be
(A) -1
(B) 2
(C) -3
(D) 0
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the answer is (A)-1
because
x^2-ax=6-----(1)
x^2+ax=2-----(2)
adding equation no.1 and 2
2x^2=8
x^2=8/2
x^2=4
by taking square root
x=2
put x=2 in equation no.2
2^2+a×2=2
4+a×2=2
a×2=2-4
a×2=-2
a=-2/2
a=-1
because
x^2-ax=6-----(1)
x^2+ax=2-----(2)
adding equation no.1 and 2
2x^2=8
x^2=8/2
x^2=4
by taking square root
x=2
put x=2 in equation no.2
2^2+a×2=2
4+a×2=2
a×2=2-4
a×2=-2
a=-2/2
a=-1
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