9x^2-10x-639=0

Solution for 9x^2-10x-639=0 equation:

9x^2-10x-639=0

a = 9; b = -10; c = -639;
Δ = b2-4ac
Δ = -102-4·9·(-639)
Δ = 23104
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{23104}=152$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-152}{2*9}=\frac{-142}{18}
=-7+8/9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+152}{2*9}=\frac{162}{18}
=9
$