112=(4-x)(28-x)

Solution for 112=(4-x)(28-x) equation:

112=(4-x)(28-x)

We move all terms to the left:

112-((4-x)(28-x))=0

We add all the numbers together, and all the variables

-((-1x+4)(-1x+28))+112=0

We multiply parentheses ..

-((+x^2-28x-4x+112))+112=0


We calculate terms in parentheses: -((+x^2-28x-4x+112)), so:

(+x^2-28x-4x+112)

We get rid of parentheses

x^2-28x-4x+112

We add all the numbers together, and all the variables

x^2-32x+112

Back to the equation:

-(x^2-32x+112)


We get rid of parentheses

-x^2+32x-112+112=0

We add all the numbers together, and all the variables

-1x^2+32x=0

a = -1; b = 32; c = 0;
Δ = b2-4ac
Δ = 322-4·(-1)·0
Δ = 1024
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1024}=32$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(32)-32}{2*-1}=\frac{-64}{-2}
=+32
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(32)+32}{2*-1}=\frac{0}{-2}
=0
$