In an obstacle course race, how many ways can five finalists be ordered?

Which is the graph of f(x) = (4)x? image for option 1 image for option 2 image for option 3 image for option 4

Ten times the square of a non-zero number is eqaul to ninety times the number

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).