(30+x)(440-10x)=0

Solution for (30+x)(440-10x)=0 equation:

(30+x)(440-10x)=0

We add all the numbers together, and all the variables

(x+30)(-10x+440)=0

We multiply parentheses ..

(-10x^2+440x-300x+13200)=0

We get rid of parentheses

-10x^2+440x-300x+13200=0

We add all the numbers together, and all the variables

-10x^2+140x+13200=0

a = -10; b = 140; c = +13200;
Δ = b2-4ac
Δ = 1402-4·(-10)·13200
Δ = 547600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{547600}=740$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(140)-740}{2*-10}=\frac{-880}{-20}
=+44
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(140)+740}{2*-10}=\frac{600}{-20}
=-30
$