5.15x^2-7.70x-0.28=0

Solution for 5.15x^2-7.70x-0.28=0 equation:

5.15x^2-7.70x-0.28=0

We add all the numbers together, and all the variables

5.15x^2-7.7x-0.28=0

a = 5.15; b = -7.7; c = -0.28;
Δ = b2-4ac
Δ = -7.72-4·5.15·(-0.28)
Δ = 65.058
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{-(-7.7)-\sqrt{65.058}}{2*5.15}=\frac{7.7-\sqrt{65.058}}{10.3}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7.7)+\sqrt{65.058}}{2*5.15}=\frac{7.7+\sqrt{65.058}}{10.3}
$