Mathematics in senior high school is an optional course 2-3. In this example, why should we separate on both sides at the same time? There are four examples to explain why the third line is?
Because x & gt=3, 4x(x- 1) is not 0, and dividing both sides by 4x(x- 1) can simplify the equation.
0 & lt= r & lt=9
0 & lt= r-2 & lt； = 9->； 2 & lt= r & lt= 1 1->； 2 & lt= r & lt=9