A(x)=x(30-2x)

Solution for A(x)=x(30-2x) equation:

(A)=A(30-2A)

We move all terms to the left:

(A)-(A(30-2A))=0

We add all the numbers together, and all the variables

A-(A(-2A+30))=0


We calculate terms in parentheses: -(A(-2A+30)), so:

A(-2A+30)

We multiply parentheses

-2A^2+30A

Back to the equation:

-(-2A^2+30A)


We get rid of parentheses

2A^2-30A+A=0

We add all the numbers together, and all the variables

2A^2-29A=0

a = 2; b = -29; c = 0;
Δ = b2-4ac
Δ = -292-4·2·0
Δ = 841
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{841}=29$
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-29)-29}{2*2}=\frac{0}{4}
=0
$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-29)+29}{2*2}=\frac{58}{4}
=14+1/2
$