What is the value of f(x) = 9x when x = -2?

Ineed in figuring out this problem.

Ricky takes out a $31,800 student loan to pay his expenses while he is in college. after graduation, he will begin making payments of $190.66 per month for the next 30 years to pay off the loan. how much more will ricky end up paying for the loan than the original value of $31,800? ricky will end up paying $ more than he borrowed to pay off the loan.

What is the point of inflection for the function f(x)=2cos4x on the interval (0, pi/2)