-5X^2-40x+165=0

Solution for -5X^2-40x+165=0 equation:

-5X^2-40X+165=0

a = -5; b = -40; c = +165;
Δ = b2-4ac
Δ = -402-4·(-5)·165
Δ = 4900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4900}=70$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-40)-70}{2*-5}=\frac{-30}{-10}
=+3
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-40)+70}{2*-5}=\frac{110}{-10}
=-11
$