Answer
{$\frac{-5-\sqrt {89}}{4}, \frac{-5+\sqrt {89}}{4}$}
Work Step by Step
$2x^2+5x-8=0$
$x^2+\frac{5x}{2}=4$
$x^2+\frac{5x}{2}+\frac{25}{16}=\frac{89}{16}$
$(x+\frac{5}{4})^2=\frac{89}{16}$
$(x+\frac{5}{4})=+\sqrt {\frac{89}{16}} or -\sqrt {\frac{89}{16}}=+{\frac{\sqrt{89}}{4}}or -{\frac{\sqrt{89}}{4}}$
x={$\frac{-5-\sqrt {89}}{4}, \frac{-5+\sqrt {89}}{4}$}