(y-y1)/(y2-y1) = (x-x1)/(x2-x1) is called a two-point equation of a straight line, but because the denominator in the formula is not 0, only one condition y2 ≠ is added. In fact, this formula can be changed into other forms, such as what you said:

y-y 1 =(Y2-y 1)/(X2-X 1)* X-X 1

This brings Y 1=Y2 in, but does not include X 1=X2.

In the point oblique type, the premise is P≠P 1, and then a graph, which he said can be verified, and then P=P 1, and this point is added. (Is that right? ) For example:

When we solve many problems, we often use algebraic operations, but we often miss many situations. For example, when the slope does not exist, we need to use the combination of numbers and shapes to supplement the solution, which is equivalent to testing. Understand this truth?

The digression is: in fact, there are many children's shoes like you, so I will be anxious with whoever says they are naive. People who only know what to do and don't know why have no brains and no life.

O(∩_∩)O~