Explain, using the theorems, why the function is continuous at every number in its domain. Q(x) = 3 x − 9 x3 − 9 Q(x) is a polynomial, so it is continuous at every number in its domain. Q(x) is a rational function, so it is continuous at every number in its domain. Q(x) is built up from functions that are continuous for all real numbers, so it is continuous at every number in its domain. Q(x) is not continuous at every number in its domain. none of these