Graph the function f(x) = 21(0.5)x. an exponential graph decreasing from the left and crossing the y axis at 0 comma 5
an exponential graph decreasing from the left and crossing the y axis at 0 comma 21
an exponential graph decreasing from the left and crossing the y axis at 0 comma 18
an exponential graph decreasing from the left and crossing the y axis at 0 comma 8