Solve for A
\left\{\begin{matrix}A=\frac{4\pi r^{2}}{a}\text{, }&a\neq 0\\A\in \mathrm{R}\text{, }&r=0\text{ and }a=0\end{matrix}\right.
Solve for a
\left\{\begin{matrix}a=\frac{4\pi r^{2}}{A}\text{, }&A\neq 0\\a\in \mathrm{R}\text{, }&r=0\text{ and }A=0\end{matrix}\right.
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aA=4\pi r^{2}
The equation is in standard form.
\frac{aA}{a}=\frac{4\pi r^{2}}{a}
Divide both sides by a.
A=\frac{4\pi r^{2}}{a}
Dividing by a undoes the multiplication by a.
Aa=4\pi r^{2}
The equation is in standard form.
\frac{Aa}{A}=\frac{4\pi r^{2}}{A}
Divide both sides by A.
a=\frac{4\pi r^{2}}{A}
Dividing by A undoes the multiplication by A.
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