For example:
The indoor temperature of each room in a hotel in Shanghai is controlled by the control room. A construction master found that the temperature displayed by the instrument in the control room was different from the actual temperature in each room. After several adjustments, it has no effect. Finally, the reason was found out. It is because the distance from the high-rise room to the control room is far away, and the three lines of three-phase electricity are different because of bending, which leads to the different resistances of the three lines and the deviation of the instrument. So how do you measure the resistance of these three wires? It is impossible for any multimeter to put one end in a room of more than ten floors and the other end in the control room on the ground floor. What should I do?
A master of algebra came up with such a way:
x？ +? y？ =? a
y？ +? z？ =? b
z？ +? x？ =? c