Does the rule y = 2 · x + 4 represent a linear or an exponential function? explain. a. linear function; the function is in the form y = abx, where a ≠ 0, b > 0, b = ≠ 1 , and x is a real number. b. linear function; the independent variable x is not an exponent. c. exponential function; the function is in the form y = mx + b, where m = slope, b = y-intercept, and x is a real number. d. exponential function; the function is in the form y = abx, where a ≠ 0, b > 0, b = ≠ 1 , and x is a real number.