Cartesian Products Of Sets

Let f(x) = x

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+ kx + 1 f '(x) = 2x + k f(x) is strictly increasing on (1, 2) if f '(x) > 0 for x

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(1, 2)

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2x + k > 0 for x

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(1, 2)

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k > -2x for x

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??(1, 2) Now, 1 < x < 2

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2 < 2x < 4

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-2 > -2x > -4

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- 4 < -2x < -2

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Hence least value of k = -2.

Chapter Questions
1 MCQs