Find the interval on the real number line for which the radicand is nonnegative (greater than or equal to zero) so that the radical $$\sqrt{3 x + 1}$$ defines a real number. Write your answer in interval notation. Note: If the answer includes more than one interval write the intervals separated by the "union" symbol, U. If needed enter $\infty$ as infinity and $-\infty$ as -infinity .
For example, you may write (-infinity, 5] for the interval $(-\infty,5]$ and (-infinity, 5]U(7,9) for $(-\infty,5]\cup(7,9)$.

Your answer: