Final answer:
The commonly used method or feature when using a calculator to find the equation of a line passing through two given points is to calculate the slope-intercept form.
Step-by-step explanation:
When using a calculator to find the equation of a line passing through two given points, the commonly used method or feature is to calculate the slope-intercept form (option C). This method involves finding the slope (m) using the formula m = (y2 - y1) / (x2 - x1), where (x1, y1) and (x2, y2) are the coordinates of the two points. Then, the equation of the line can be written in the form y = mx + b, where m is the slope and b is the y-intercept.