1.3X^2+0.8x-0.7=0

Solution for 1.3X^2+0.8x-0.7=0 equation:

1.3X^2+0.8X-0.7=0

a = 1.3; b = 0.8; c = -0.7;
Δ = b2-4ac
Δ = 0.82-4·1.3·(-0.7)
Δ = 4.28
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{-(0.8)-\sqrt{4.28}}{2*1.3}=\frac{-0.8-\sqrt{4.28}}{2.6}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0.8)+\sqrt{4.28}}{2*1.3}=\frac{-0.8+\sqrt{4.28}}{2.6}
$