1.

25. The integer k for which the inequality `x^2 -2(4k 1)x 15k 2k-7 0 is valid for any real x is (2) 3 (3) 4 (4) 5A. 2B. 3C. 4D. none of these

Answer» Correct Answer - B
Let `f(x) = x^(2) - 2(4k -1)x+15k^(2) - 2k -7`. Then, `f(x) gt 0` for all x `in` R
`rArr" ""Disc" lt 0`
`rArr" "4(4k-1)^(2)-4(15k^(2)-2k-7) lt 0`
`rArr" "k^(2)-6k + 8 lt 0 rArr 2 lt k lt 4`


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