0.81x^2-1.3x-2.35=0

Solution for 0.81x^2-1.3x-2.35=0 equation:

0.81x^2-1.3x-2.35=0

a = 0.81; b = -1.3; c = -2.35;
Δ = b2-4ac
Δ = -1.32-4·0.81·(-2.35)
Δ = 9.304
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{-(-1.3)-\sqrt{9.304}}{2*0.81}=\frac{1.3-\sqrt{9.304}}{1.62}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.3)+\sqrt{9.304}}{2*0.81}=\frac{1.3+\sqrt{9.304}}{1.62}
$