Which of the following functions functions has a rate of change that stays the same?y=1/3x^2 y=2xy=-7x+9y=x^2+1

Answer:y = 2x   and y = -7x +9Step-by-step explanation:The two "linear" functions are those that have a constant rate of change. Actually, the slope (inclination) they show when plotted is that "rate of change". The function : y = 2x, has a constant positive rate given by its slope (2).The function : y= -7x +9 has a constant negative rate given by its slope (-7)The other two functions are quadratic, represented by parabolas, and therefore don't have a constant rate of change.