x^2-0.9x-0.7=0

Solution for x^2-0.9x-0.7=0 equation:

x^2-0.9x-0.7=0

a = 1; b = -0.9; c = -0.7;
Δ = b2-4ac
Δ = -0.92-4·1·(-0.7)
Δ = 3.61
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{-(-0.9)-\sqrt{3.61}}{2*1}=\frac{0.9-\sqrt{3.61}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.9)+\sqrt{3.61}}{2*1}=\frac{0.9+\sqrt{3.61}}{2}
$