A=-2w(w-10)

Solution for A=-2w(w-10) equation:

=-2A(A-10)

We move all terms to the left:

-(-2A(A-10))=0


We calculate terms in parentheses: -(-2A(A-10)), so:

-2A(A-10)

We multiply parentheses

-2A^2+20A

Back to the equation:

-(-2A^2+20A)


We get rid of parentheses

2A^2-20A=0

a = 2; b = -20; c = 0;
Δ = b2-4ac
Δ = -202-4·2·0
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-20}{2*2}=\frac{0}{4}
=0
$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+20}{2*2}=\frac{40}{4}
=10
$