90x^2+71x-9=0

Solution for 90x^2+71x-9=0 equation:

90x^2+71x-9=0

a = 90; b = 71; c = -9;
Δ = b2-4ac
Δ = 712-4·90·(-9)
Δ = 8281
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{8281}=91$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(71)-91}{2*90}=\frac{-162}{180}
=-9/10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(71)+91}{2*90}=\frac{20}{180}
=1/9
$