Solve the equation by using the Square Root Property. $9u^2+30=0$

A) $u=\pm \sqrt{30}$
B) $u=\pm \frac{\sqrt{30}}{9}i$
C) $u=\pm \frac{\sqrt{30}}{3}$
D) $u=\pm \frac{\sqrt{30}}{9}$
E) $u=\pm \frac{\sqrt{30}}{3}i$

To use the Square Root Property, we need to isolate the variable, which means we need to move the constant term to the other side of the equation:
$$\begin{array}{rl}9u^2& =-30\\ u^2& =-\frac{30}{9}\\ u^2& =-\frac{10}{3}\end{array}$$
However, since we cannot take the square root of a negative number in the real number system, we have to use imaginary numbers. The square root of $-1$ is denoted by $i$, so we have:
$$\begin{array}{rl}u& =\pm \sqrt{-\frac{10}{3}}\\ & =\pm \sqrt{\frac{-10}{3}}\\ & =\pm \sqrt{\frac{-10}{3}\cdot \frac{3}{3}}\\ & =\pm \sqrt{\frac{-30}{9}}\\ & =\pm \frac{\sqrt{30}}{\sqrt{9}}\cdot \sqrt{-1}\\ & =\pm \frac{\sqrt{30}}{3}i\end{array}$$
Therefore, the answer is E.