Functions are tools you can combine: add them, multiply them or feed one into another. Shift, stretch and flip any graph with f(x) + k, f(x + k), kf(x) and -f(x). Compare two functions given in different ways, measure average rate of change over an interval, and read where f(x) = g(x) from a graph, a table or by solving. A line meets a parabola where their rules agree.