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# Pls help

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

Oct 22, 2020

### 1+0 Answers

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

Hello Guest!

$$f(x)=4(x + 7)(2 - x)\\ f(x)=4(2x-x^2+14-7x)\\ f(x)=-4x^2-20x+56\\ \frac{df(x)}{dx}=-8x-20=0\\ x_{min}=-2.5\\\color{blue} f(x)_{max}=81$$,

The maximum value of $$4(x + 7)(2 - x)$$ is 81.

!

Oct 22, 2020
edited by asinus  Oct 22, 2020
edited by asinus  Oct 22, 2020
edited by asinus  Oct 22, 2020