(4+1.10x)(300-5x)=0

Solution for (4+1.10x)(300-5x)=0 equation:

(4+1.10x)(300-5x)=0

We add all the numbers together, and all the variables

(1.10x+4)(-5x+300)=0

We multiply parentheses ..

(-5x^2+300x-20x+1200)=0

We get rid of parentheses

-5x^2+300x-20x+1200=0

We add all the numbers together, and all the variables

-5x^2+280x+1200=0

a = -5; b = 280; c = +1200;
Δ = b2-4ac
Δ = 2802-4·(-5)·1200
Δ = 102400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{102400}=320$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(280)-320}{2*-5}=\frac{-600}{-10}
=+60
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(280)+320}{2*-5}=\frac{40}{-10}
=-4
$