If f(x) = x2, which of the following describes the graph of f(x) + 4? the graph of f(x) + 4 is a vertical shift of f(x) = x2 four units up. the graph of f(x) + 4 is a vertical shift of f(x) = x2 four units down. the graph of f(x) + 4 is a horizontal shift of f(x) = x2 four units to the right. the graph of f(x) + 4 is a horizontal shift of f(x) = x2 four units to the left.