y = f(x) + c is the graph y = f(x) shifted upward c units.
y = f(x) - c is the graph of y = f(x) shifted downward c units.
y = f(x - c) is the graph of y = f(x) shifted to the right c units.
y = f(x + c ) is the graph of y = f(x) shifted to the left c units.
