A function of x is given by f(x) = 2x - 3. which of these describes the meaning of f(-1)? a. the output value for the function f when x = -1 b. the output value for the function of f when 2 is added to -3. c. the input value for the function f when x = -1 d. the output value for the function f when 2 is added to -3.