(2-a)(4-a)=0

Solution for (2-a)(4-a)=0 equation:

(2-a)(4-a)=0

We add all the numbers together, and all the variables

(-1a+2)(-1a+4)=0

We multiply parentheses ..

(+a^2-4a-2a+8)=0

We get rid of parentheses

a^2-4a-2a+8=0

We add all the numbers together, and all the variables

a^2-6a+8=0

a = 1; b = -6; c = +8;
Δ = b2-4ac
Δ = -62-4·1·8
Δ = 4
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4}=2$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6)-2}{2*1}=\frac{4}{2}
=2
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6)+2}{2*1}=\frac{8}{2}
=4
$