Enter an exact number. Submit Answer 19. [-/2 Points] DETAILS SCALC8 1.8.025. Explain, using the theorems, why the function is continuous at every number in its domain. F ( x ) = 2x2 - x - 9 x2 + 9 O F(x) is a polynomial, so it is continuous at every number in its domain. O F(x) is a rational function, so it is continuous at every number in its domain. O F(x) is a composition of functions that are continuous for all real numbers, so it is continuous at every number in its domain. O F(x) is not continuous at every number in its domain. O none of these State the domain. (Enter your answer using interval notation.)