The formule is about area of a circle.
[tex]\pi x^{2} = a[/tex]
We need to solve the equation for x. Where x is the radius of the circle.
In order to solve it for x, we need isolate it for x on left side.
So, first we need to get rid pi from left side.
On dividing both sides by pi, we get
[tex]\frac{\pi x^2}\pi}=\frac{a}{\pi}[/tex]
[tex]x^2=\frac{a}{\pi}[/tex]
Taking square root on both sides, we get
[tex]\sqrt{x^2}=\sqrt{\frac{a}{\pi}}[/tex]
[tex]x=\sqrt{\frac{a}{\pi}}[/tex]
