(55-x)(40-x)=0

Solution for (55-x)(40-x)=0 equation:

(55-x)(40-x)=0

We add all the numbers together, and all the variables

(-1x+55)(-1x+40)=0

We multiply parentheses ..

(+x^2-40x-55x+2200)=0

We get rid of parentheses

x^2-40x-55x+2200=0

We add all the numbers together, and all the variables

x^2-95x+2200=0

a = 1; b = -95; c = +2200;
Δ = b2-4ac
Δ = -952-4·1·2200
Δ = 225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{225}=15$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-95)-15}{2*1}=\frac{80}{2}
=40
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-95)+15}{2*1}=\frac{110}{2}
=55
$