中等MATH-ALGE-004
Make r the subject of A = π r^2, where r > 0.
A. r = A / π
B. r = √A / π
C. r = √(A / π)✓ 答案
D. r = A^2 / π
解說
Divide both sides by π first, then take the positive square root: r = √(A/π). In √A / π the division by π happens after the root, so it is a different expression.