To find the minimum value of (f(x) = \frac{x^2 + 2x + 4}{x + 1}) where (x > -1), follow these steps:
Step 1: Simplify the function
Let (t = x + 1) (since (x > -1), (t > 0)). Then (x = t - 1). Substitute into the function:
[
f(x) = \frac{(t - 1)^2 + 2(t - 1) + 4}{t}
]
Expand the numerator:
[
(t^2 - 2t + 1) + 2t - 2 + 4 = t^2 + 3
]
Thus:
[
f(x) = \frac{t^2 + 3}{t} = t + \frac{3}{t}
]
Step 2: Apply AM-GM inequality
For positive (t), the Arithmetic Mean-Geometric Mean inequality gives:
[
t + \frac{3}{t} \geq 2\sqrt{t \cdot \frac{3}{t}} = 2\sqrt{3}
]
Equality holds when (t = \frac{3}{t}), i.e., (t^2 = 3) → (t = \sqrt{3}) (since (t > 0)).
Step 3: Confirm the minimum value
Substitute (t = \sqrt{3}) back to (x): (x = \sqrt{3} - 1) (which is > -1). The minimum value is (2\sqrt{3}).
Answer: (\boxed{2\sqrt{3}})

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