The function g is a function of the form g x = a · b x , where a ≠ 0 and b > 0 . ​The function f is given by f x = g x + 4 . Which of the following statements is true? Responses ​The output values of both f and g are proportional over equal-length input-value intervals. ​The output values of both f and g are proportional over equal-length input-value intervals. ​​The output values of f only, not g , are proportional over equal-length input-value intervals. ​​The output values of f only, not g , are proportional over equal-length input-value intervals. ​​​The output values of g only, not f , are proportional over equal-length input-value intervals. ​​​The output values of g only, not f , are proportional over equal-length input-value intervals. ​​The output values of neither f nor g are proportional over equal-length input-value intervals.