How to change x-scale/y-scale of the coordinates system

Different x-scale/y-scale of the coordinates system makes different looks of the graph of the same function. The following pictures show the graph of the same polynomial with two different values of x-scale:

Graph with bigger x-scale

Graph with smaller x-scale

Sometimes you need to change x-scale or y-scale to make the graph more appropriated for your requirements. Touch on the "x-scale" or "y-scale" circle to do that:

Tap on the green circle to change x-scale

There are 6 options of the scales from the smallest "+" to the biggest "++++++", simply touch to choose!