The set of values of a for which (a−1)x2−(a+1)x+a−1≥0 is true for all x≥2 is
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a
(−∞,1)
b
1,73
c
73,∞
d
none of these
answer is C.
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Detailed Solution
Given,(a−1)x2−(a+1)x+a−1≥0or ax2−x+1−x2+x+1≥0⇒ a≥x2+x+1x2−x+1=1+2xx2−x+1=1+2x+1x−1 (1)Let y=x+1/x. Now, y is increasing in [2,∞). Hence1+2x+1x−1∈1,73For all x≥2 Eq. ( 1) should be true. Hence, a > 7/3 .