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# Pls help reposted from yesterday

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What is the maximum value of $4(x + 7)(2 - x)$, over all real numbers $x$?

Oct 22, 2020

First, convert into vertex form by first foiling (x+7) and (2-x), which turns the equation into  $$4(-x^2-7x+2x+14)$$ = $$4(-x^2-5x+14) = -4x^2-20x+56$$. Then, use -b/2a to find the x-coordinate of the vertex $$20 \over 2*-4$$=-5/2. Then, just plug -5/2 into the equation to get the y-coordinate. The vertex in this case is the maximum of because the leading coefficient is negative for a quadratic equation.