The function concept arose from analyzing the relationships between co-varying quantities to model change. From the covariation perspective of function, we analyzed the responses of 13 pre-service teachers to the tasks to interpret rates of change or reason the corresponding change of one quantity from the changes of the other using the given rate of change; by using the rate of change, a change of one quantity can be directly deduced from the given change of the other quantity. Most of the pre-service teachers reasoned the change correctly. However, a portion of pre-service teachers reflexively calculated the formula of the function and the difference between the two values of the function. In addition, some teachers revealed their insufficient understanding of the slope of the linear function. The conceptions of pre-service teachers help elucidate what and how students might learn and might not learn about functions from the school mathematics curriculum.

Keywords함수,변화율,변화량,공변,function,rate of change,change in quantity,covariation