# How do you solve 7x^2+10x=2x^2+155 using any method?

Aug 12, 2016

$x = 4 \sqrt{2} - 1$ or $x = 4 \sqrt{2} + 1$

#### Explanation:

$7 {x}^{2} + 10 x = 2 {x}^{2} + 155$

$\Leftrightarrow 7 {x}^{2} + 10 x - 2 {x}^{2} - 155 = 0$ or

$5 {x}^{2} + 10 x - 155 = 0$ and dividing by $5$

${x}^{2} + 2 x - 31 = 0$

and using quadratic formula $\frac{- b \pm \sqrt{{b}^{2} - 4 a c}}{2} a$ , as we have here $a = 1$, $b = 2$ and $c = - 31$

x=(-2+-sqrt((-2)^2-4×1×(-31)))/(2×1) or

x=(-2+-sqrt(4+124))/(2×1) or

$x = \frac{- 2 \pm \sqrt{128}}{2}$ or

$x = \frac{- 2 \pm 8 \sqrt{2}}{2} = - 1 \pm 4 \sqrt{2}$ or

$x = 4 \sqrt{2} - 1$ or $x = 4 \sqrt{2} + 1$