Q.
Set of all real values of a such that f(x)=(2a−1)x2+2(a+1)x+(2a−1)x2−2x+40is always negative is
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a
(−∞,0)
b
(0,∞)
c
(−∞,1/2)
d
None
answer is A.
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Detailed Solution
f(x)=(2a−1)x2+2(a+1)x+(2a−1)x2−2x+40 Since x2−2x+40>0 for all real x, (2a−1)x2+2(a+1)x+(2a−1)<0∀x∈R∴ 2a−1<0 or a<12 and D<0 (1)⇒ 4(a+1)2−4(2a−1)2<0⇒ a(a−2)>0⇒ a<0 or a>2 (2)From (1) and (2), a <0
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