7x2-13x-90=0

Solution for 7x2-13x-90=0 equation:

7x^2-13x-90=0

a = 7; b = -13; c = -90;
Δ = b2-4ac
Δ = -132-4·7·(-90)
Δ = 2689
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{-(-13)-\sqrt{2689}}{2*7}=\frac{13-\sqrt{2689}}{14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-13)+\sqrt{2689}}{2*7}=\frac{13+\sqrt{2689}}{14}
$