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Error-prone points of mathematics in the second volume of seventh grade
Landlord, let me distinguish it carefully for you, please pay attention.

The (1) fraction mainly focuses on the simplification and re-evaluation of the fraction. Attention should be paid to the denominator of this kind of problem, and we can't make an appointment casually. Only when the numerator and denominator of a fraction have common factors can it be simplified and the denominator can be removed (it can't be removed in general, which is specially set by others).

For example: (x? The fraction-1)/ (x- 1) is = x+ 1, and the denominator is missing. In fact, the original formula =

(x+1) (x- 1)/(x-1) = x+1,that is, the common factor x-1of the numerator and denominator is omitted.

But (x? - 1)/ (x - 1)= x? -1 no! ! ! ! ! You removed the denominator for no reason! ! ! ! ! There must be a mistake! ! ! ! !

Remember: the denominator cannot be removed at will! ! ! ! ! ! ! ! ! ! You should strictly follow the four algorithms of fractions. For example, the addition and subtraction of fractions, we must first find the simplest common denominator, do a rough division, become the addition and subtraction of fractions with the same denominator, and then operate.

(2) Fractional equation: The denominator must be removed. The basis of naming: the basic properties of equations.

For example: 6/x+3/(x-1) = 7/(x-1)

First, know that the simplest common denominator is x (x-1); Then multiply the left and right ends of the fractional equation by x (x- 1).

6 (x- 1)+ 3 x = 7 x (this step uses the basic properties of the equation); I believe you can solve the whole equation in the future!

Difference: the simplification of the score is only a score at first, not an equal sign (=), and the equal sign is added by you. So we can't talk about the denominator, and we can't use the basic properties of the equation;

The fractional equation is different. At first, it is an equation with an equal sign (=). Therefore, you can use the basic properties of the equation to name it.

I hope it will help you, and your affirmation is my motivation! ! ! ! ! ! !