# How do you solve -2x^2-80=0?

Nov 8, 2016

$x = \pm 2 \sqrt{10} i$

#### Explanation:

$- 2 {x}^{2} - 80 = 0$

$\rightarrow {x}^{2} + 40 = 0$

$\rightarrow {x}^{2} = - 40 = {i}^{2} \cdot {2}^{2} \cdot 10$

$\rightarrow x = \pm i 2 \sqrt{10} \mathmr{and} \pm 2 \sqrt{10} i$

Nov 8, 2016

$- 2 {x}^{2} - 80 = 0$

Usually you would want a quadratic equation to be equal to 0, but in this case there is no $x$ term, so we will solve it by another method.

Re-arrange to give:

$- 2 {x}^{2} = 80 \text{ } \leftarrow \div - 2$

${x}^{2} = - 40$

$x = \pm \sqrt{- 40}$

There are no real solutions to this equation.