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How do you solve $8 x - x^{2} = 15$ $8x - x^2 = 15$ ?

1 Answer

Jan 22, 2016

Re-write the equation in standard form; then factor to get
$XXX x = 3$ $color(white)("XXX")x=3$ or $x = 5$ $x=5$

Explanation:

$8 x - x^{2} = 15$ $8x-x^2=15$

$\Leftrightarrow x^{2} - 8 x + 15 = 0$ $hArr x^2-8x+15=0$

$\Leftrightarrow (x - 3) (x - 5) = 0$ $hArr (x-3)(x-5)=0$

$(x - 3) = 0 \to x = 3$ $(x-3)=0 rarr x=3$
or
$(x - 5) = 0 \to x = 5$ $(x-5)=0 rarr x=5$

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