A=(14-2x)(18-2x)

Solution for A=(14-2x)(18-2x) equation:

=(14-2A)(18-2A)

We move all terms to the left:

-((14-2A)(18-2A))=0

We add all the numbers together, and all the variables

-((-2A+14)(-2A+18))=0

We multiply parentheses ..

-((+4A^2-36A-28A+252))=0


We calculate terms in parentheses: -((+4A^2-36A-28A+252)), so:

(+4A^2-36A-28A+252)

We get rid of parentheses

4A^2-36A-28A+252

We add all the numbers together, and all the variables

4A^2-64A+252

Back to the equation:

-(4A^2-64A+252)


We get rid of parentheses

-4A^2+64A-252=0

a = -4; b = 64; c = -252;
Δ = b2-4ac
Δ = 642-4·(-4)·(-252)
Δ = 64
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{64}=8$
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(64)-8}{2*-4}=\frac{-72}{-8}
=+9
$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(64)+8}{2*-4}=\frac{-56}{-8}
=+7
$