Help me please with this question

Answer:
[tex]y = \sqrt{ \frac{\pi \: x - A {}^{} }{\pi} } [/tex]
Step-by-step explanation:
To make y subject of formular, we place y in terms of other variables.
[tex] A = \pi \: x {}^{2} - \pi \: y {}^{2} \\ making \: y \: subject \\ A + \pi \: y {}^{2} = \pi \: x {}^{2} \\ \pi \: y {}^{2} = \pi \: x {}^{2} - A \\ Dividing \: bothsides \: by \: \pi \\ y {}^{2} = \frac{\pi \: x { - A}^{} }{\pi} \\ Squarerooting \: bothsides \\ y = \sqrt{ \frac{\pi \: x - A {}^{} }{\pi} } [/tex]