(x-40)*(x-60)=0

Solution for (x-40)*(x-60)=0 equation:

(x-40)(x-60)=0

We multiply parentheses ..

(+x^2-60x-40x+2400)=0

We get rid of parentheses

x^2-60x-40x+2400=0

We add all the numbers together, and all the variables

x^2-100x+2400=0

a = 1; b = -100; c = +2400;
Δ = b2-4ac
Δ = -1002-4·1·2400
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-100)-20}{2*1}=\frac{80}{2}
=40
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-100)+20}{2*1}=\frac{120}{2}
=60
$