PLEASE HELP!

Which of the following is a monomial?

What is the vertex form of f(x) = x2 + 6x + 3

Suppose that 3% of all athletes are using the endurance-enhancing hormone epo (you should be able to simply compute the percentage of all athletes that are not using epo). for our purposes, a “positive” test result is one that indicates presence of epo in an athlete’s bloodstream. the probability of a positive result, given the presence of epo is .99. the probability of a negative result, when epo is not present, is .90. what is the probability that a randomly selected athlete tests positive for epo? 0.0297

What is the solution to this system of equations? y= 2x - 3.5 x - 2y = -14