Solve the equation and choose the BEST answer: \(\frac{\mathrm{9} }{\mathrm{b}} = \frac{\mathrm{b} }{\mathrm{4}}\)

Cross-multiply: \(9 \times 4 = b \times b\)
\(36=b^2\)
Then, find the square root of both sides:
The actual square root of \(b^2\) is \(\pm b\) and the actual square root of 36 is \(\pm b\), so:
\(b= \pm 6\)
Of the answer choices for this question, 6 is the best choice since it is the only one that is true about the equation.