Find the minimum value of to 3 decimal places.
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If f ( x ) = x 2 + 2 x + 2 , then f ′ ( x ) = 2 x + 2 x ⋅ l n ( 2 ) = 0 ⇒ x + 2 x − 1 ⋅ l n ( 2 ) = 0 ⇒ 2 x ⋅ l n ( 2 ) = − x . This exponential curve and line must intersect in the second quadrant of the x y − plane. At x = − 1 we obtain 2 − 1 ⋅ l n ( 2 ) ≈ 0 . 1 7 3 3 for the LHS and 1 for the RHS, which implies the critical point must lie within x ∈ ( − 1 , 0 ) . After some trial-&-error I find the critical value to be x ≈ − 0 . 2 8 4 5 , and f ′ ′ ( x ) = 2 + 2 x ⋅ ( l n ( 2 ) ) 2 > 0 for all real x . So the minimum value of f ( x ) computes to ( − 0 . 2 8 4 5 ) 2 + 2 − 0 . 2 8 4 5 + 2 ≈ 2 . 9 0 4 .