Question

Solve the formula for the indicated variable.
A = 4πr² for r when r > 0

r =

Answer 1

r =
`\sqrt{(A)/(4\pi ) }`

Explanation:

Given

A = 4πr² ( isolate r² by dividing both sides by 4π )

r² =
`(A)/(4\pi )`

Take the square root of both sides

r =
`\sqrt{(A)/(4\pi ) }`

Answer 2

√(A/4π) = r

Explanation:

A = 4πr²

r² = A/4π

r = √(A/4π)