Explanation:
x^2 + 4x + 8 = (x^2 + 4x + 4) + 4 = (x + 2)^2 + 4.
When x^2 + 4x + 8 > 5, this means (x + 2)^2 + 4 > 5.
So (x + 2)^2 > 1.
=> (x + 2) > 1 or (x + 2) < -1.
=> x > -1 or x < -3.
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