Let f(x) = (1 – x)2 sin2x + x2 R and let g(x) =
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Consider the statements :
P : There exists some x R such that f(x) + 2x = 2 (1 + x2).
Q : There exist some x R such that 2f(x) + 1 = 2x (1 + x).
Then
Let F(x) = f(x) + 2x – 2 – 2x2
F(x) = (1 – x)2 sin2x + x2 + 2x – 2 – 2x2
F(x) = (1 – x)2 sin2x – (1 – x)2 – 1
F(x) = – (1 – x)2 cos2x – 1 = – 1 [(1 – x)2cos2x + 1]
F(x) < 0 F (x) = 0 is not possible for any x R. So P is false
Let G(x) = 2f(x) + 1 – 2x – 2x2
G(x) = 2(1 – x)2 sin2x + 2x2 + 1 – 2x – 2x2
G(x) = 2 [1 – 2x + x2] sin2x + (1 – 2x)
G(x) = (2sin2x + 1) (1 – 2x) + 2x2 sin2x
Now G (x) = 0 sin2x =
As [– 1/2, ), so Q is true.
Hence P is false and Q is true.
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Which of the following is true?
Consider h(x) = 2 – – ln x
h'(x) =
h'(x) =
h'(x) = < 0
h(x) is a decreasing function (1, )
h(x) < h(1) = 0
h(x) < 0 (1, )
g(x) < 0 as f(x) > 0 g(x) is decreasing in x (1, ). Ans.
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