For real x, what is the greatest value of 12 + 6x − x²?

21. 12 + 6x − x² = 21 − (x − 3)². The square is never negative, so the greatest value is 21, at x = 3.

For real $x$ , what is the greatest value of $12 + 6 x - x^{2}$ ?

Competition practiceAlgebra

12 + 6 x - x^{2} = 21 - (x - 3)^{2}

. The square is never negative, so the greatest value is 21, at

x = 3

Answer: A) 21

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