(X-40)(x-10)=0

Solution for (X-40)(x-10)=0 equation:

(X-40)(X-10)=0

We multiply parentheses ..

(+X^2-10X-40X+400)=0

We get rid of parentheses

X^2-10X-40X+400=0

We add all the numbers together, and all the variables

X^2-50X+400=0

a = 1; b = -50; c = +400;
Δ = b2-4ac
Δ = -502-4·1·400
Δ = 900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{900}=30$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-50)-30}{2*1}=\frac{20}{2}
=10
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-50)+30}{2*1}=\frac{80}{2}
=40
$