If f(x)=4x^3-24x^2-31x+21 and f(7)=0 then find all of the zeros of f(x) algebraically

The total cost of anja’s trip to the dentist was $628.35. she paid a flat fee of $89.95 which included the checkup and cleaning and then had 4 cavities filled, each of which cost the same amount. which shows the correct equation and value of x, the cost of each cavity filling?

Can someone me out here and the tell me the greatest common factor

Bring the fraction a/a-4 to a denominator of 16-a^2