(5x+1)(x+9)=0

Solution for (5x+1)(x+9)=0 equation:

(5x+1)(x+9)=0

We multiply parentheses ..

(+5x^2+45x+x+9)=0

We get rid of parentheses

5x^2+45x+x+9=0

We add all the numbers together, and all the variables

5x^2+46x+9=0

a = 5; b = 46; c = +9;
Δ = b2-4ac
Δ = 462-4·5·9
Δ = 1936
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1936}=44$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(46)-44}{2*5}=\frac{-90}{10}
=-9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(46)+44}{2*5}=\frac{-2}{10}
=-1/5
$