Question 292545
That's the exact answer. 
You can get an approximate decimal answer if you like.
{{{x1=(5+sqrt(89))/4=3.61}}}

{{{x2=(5-sqrt(89))/4=-1.11}}}
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and then check your solution graphically,
{{{ graph( 300, 300, -5, 5, -10, 10,2x^2-5x-8) }}}