(8+x)(4x+9)=0

Solution for (8+x)(4x+9)=0 equation:

(8+x)(4x+9)=0

We add all the numbers together, and all the variables

(x+8)(4x+9)=0

We multiply parentheses ..

(+4x^2+9x+32x+72)=0

We get rid of parentheses

4x^2+9x+32x+72=0

We add all the numbers together, and all the variables

4x^2+41x+72=0

a = 4; b = 41; c = +72;
Δ = b2-4ac
Δ = 412-4·4·72
Δ = 529
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{529}=23$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(41)-23}{2*4}=\frac{-64}{8}
=-8
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(41)+23}{2*4}=\frac{-18}{8}
=-2+1/4
$