# How do you solve 2y^2 – 6y – 8 = 0 using the quadratic formula?

Sep 17, 2016

$y = - 1 \text{; } y = 4$

#### Explanation:

Just use $y$ instead of $x$

$\textcolor{b r o w n}{\text{Given: } x = 2 {y}^{2} - 6 y - 8 = 0}$

$a = 2 \text{; "b=-6"; } c = - 8$

$x = a {y}^{2} + b y + c$

Where: $\text{ } y = \frac{- b \pm \sqrt{{b}^{2} - 4 a c}}{2 a}$

$\implies y = \frac{+ 6 \pm \sqrt{{6}^{2} - 4 \left(2\right) \left(- 8\right)}}{2 \left(2\right)}$

$y = \frac{6}{4} \pm \frac{\sqrt{100}}{4}$

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$\textcolor{b r o w n}{y = \frac{6}{4} + \frac{10}{4} = \frac{16}{4} = 4}$

$\textcolor{b r o w n}{y = \frac{6}{4} - \frac{10}{4} = - \frac{4}{4} = - 1}$