(x+9)(x+10)=0

Solution for (x+9)(x+10)=0 equation:

(x+9)(x+10)=0

We multiply parentheses ..

(+x^2+10x+9x+90)=0

We get rid of parentheses

x^2+10x+9x+90=0

We add all the numbers together, and all the variables

x^2+19x+90=0

a = 1; b = 19; c = +90;
Δ = b2-4ac
Δ = 192-4·1·90
Δ = 1
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1}=1$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(19)-1}{2*1}=\frac{-20}{2}
=-10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(19)+1}{2*1}=\frac{-18}{2}
=-9
$