A=3.14R^2-3.14r^2

Solution for A=3.14R^2-3.14r^2 equation:

=3.14^2-3.14A^2

We move all terms to the left:

-(3.14^2-3.14A^2)=0

We get rid of parentheses

3.14A^2-3.14^2=0

We add all the numbers together, and all the variables

3.14A^2-9.8596=0

a = 3.14; b = 0; c = -9.8596;
Δ = b2-4ac
Δ = 02-4·3.14·(-9.8596)
Δ = 123.836576
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-\sqrt{123.836576}}{2*3.14}=\frac{0-\sqrt{123.836576}}{6.28}
=-\frac{\sqrt{}}{6.28}
$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{123.836576}}{2*3.14}=\frac{0+\sqrt{123.836576}}{6.28}
=\frac{\sqrt{}}{6.28}
$