How do you solve $x^{2} + 10 x = 15$ $x^ { 2} + 10x = 15$ ?

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How do you solve $x^{2} + 10 x = 15$ $x^ { 2} + 10x = 15$ ?

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Answer 1 · 2017-06-04T23:07:22

$x = - 5 \pm 2 \sqrt{10}$ $x=-5+-2sqrt10$

Explanation:

$x^{2} + 10 x = 15$ $x^2+10x=15$
$x^{2} + 10 x - 15 = 0$ $x^2+10x-15=0$

Apply factoring (what multiplies to -15 and adds up to 10?)
if no answer, then proceed to quadratic equation

$x = \frac{- b \pm \sqrt{b^{2} - 4 a c}}{2 a}$ $x=(-b+-sqrt(b^2-4ac))/(2a)$
$x = \frac{- 10 \pm \sqrt{10^{2} - 4 \cdot 1 \cdot - 15}}{2 \cdot 1}$ $x=(-10+-sqrt(10^2-4*1*-15))/(2*1)$
$x = \frac{- 10 \pm \sqrt{160}}{2}$ $x=(-10+-sqrt160)/(2)$
$x = \frac{- 10 \pm 4 \sqrt{10}}{2}$ $x=(-10+-4sqrt10)/(2)$
$x = - 5 \pm 2 \sqrt{10}$ $x=-5+-2sqrt10$

It's long at first, but after a while, you'll get the hang of it and you can do it in your head

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How do you solve $x^{2} + 10 x = 15$ $x^ { 2} + 10x = 15$ ?

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How do you solve $x^{2} + 10 x = 15$ $x^ { 2} + 10x = 15$ ?