Consider the function. f (x) = 6x √x² +1 Identify the domain of f. (Give your answer as an interval in the form (*,*). Use the symbol [infinity] for infinity, U for combining intervals, and an appropriate type of parentheses "(",")", "[", or "]" depending on whether the interval is open or closed. Enter Ø if the interval is empty. Express numbers in exact form. Use symbolic notation and fractions where needed.) domain of f: