Which function has a vertex at the origin
a) f(x)= (x+4)^2
b) f(x)= x(x-4)
c) f(x)= (x-4)(x+4)
d) f(x)= x^2

There are three bags: a (contains 2 white and 4 red balls), b (8 white, 4 red) and c (1 white 3 red). you select one ball at random from each bag, observe that exactly two are white, but forget which ball came from which bag. what is the probability that you selected a white ball from bag a?