X^2+0.28x-0.84=0

Solution for X^2+0.28x-0.84=0 equation:

X^2+0.28X-0.84=0

a = 1; b = 0.28; c = -0.84;
Δ = b2-4ac
Δ = 0.282-4·1·(-0.84)
Δ = 3.4384
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{-(0.28)-\sqrt{3.4384}}{2*1}=\frac{-0.28-\sqrt{3.4384}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0.28)+\sqrt{3.4384}}{2*1}=\frac{-0.28+\sqrt{3.4384}}{2}
$