-10x^2+91x-9=0

Solution for -10x^2+91x-9=0 equation:

-10x^2+91x-9=0

a = -10; b = 91; c = -9;
Δ = b2-4ac
Δ = 912-4·(-10)·(-9)
Δ = 7921
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{7921}=89$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(91)-89}{2*-10}=\frac{-180}{-20}
=+9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(91)+89}{2*-10}=\frac{-2}{-20}
=1/10
$