A=-(x2-40x)

Solution for A=-(x2-40x) equation:

=-(A2-40A)

We move all terms to the left:

-(-(A2-40A))=0

We add all the numbers together, and all the variables

-(-(+A^2-40A))=0


We calculate terms in parentheses: -(-(+A^2-40A)), so:

-(+A^2-40A)

We get rid of parentheses

-A^2+40A

We add all the numbers together, and all the variables

-1A^2+40A

Back to the equation:

-(-1A^2+40A)


We get rid of parentheses

1A^2-40A=0

We add all the numbers together, and all the variables

A^2-40A=0

a = 1; b = -40; c = 0;
Δ = b2-4ac
Δ = -402-4·1·0
Δ = 1600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1600}=40$
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-40)-40}{2*1}=\frac{0}{2}
=0
$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-40)+40}{2*1}=\frac{80}{2}
=40
$