9-x^2-8x=0

Solution for 9-x^2-8x=0 equation:

9-x^2-8x=0

We add all the numbers together, and all the variables

-1x^2-8x+9=0

a = -1; b = -8; c = +9;
Δ = b2-4ac
Δ = -82-4·(-1)·9
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-10}{2*-1}=\frac{-2}{-2}
=1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+10}{2*-1}=\frac{18}{-2}
=-9
$