5x^2-x-0.8=0

Solution for 5x^2-x-0.8=0 equation:

5x^2-x-0.8=0

We add all the numbers together, and all the variables

5x^2-1x-0.8=0

a = 5; b = -1; c = -0.8;
Δ = b2-4ac
Δ = -12-4·5·(-0.8)
Δ = 17
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-1)-\sqrt{17}}{2*5}=\frac{1-\sqrt{17}}{10}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1)+\sqrt{17}}{2*5}=\frac{1+\sqrt{17}}{10}
$