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Question
Find the value of x, such that f(x) is increasing function.
f(x) = x2 + 2x - 5
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Solution
f(x) = x2 + 2x - 5
∴ f'(x) = 2x + 2
f(x) is an increasing function, if f'(x) > 0
∴ 2x + 2 > 0
∴ 2x > -2
∴ x > - 1
Thus, f(x) is an increasing function for x > -1, i.e., (-1, ∞)
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