I. Equations (groups) and inequalities (groups)

1, the solutions of various equations (groups) should be mastered skillfully, and the meaning of no solution of equations (groups) is that the conditions for the establishment of equations cannot be found.

2. When using the properties of the equation, we should pay attention to the situation that both sides are divided by a number, and also pay attention to solving the equation and the basic idea of the equation. The main trap of elimination and reduction is the time reversal test of eliminating an x common factor.

3. When applying the property of inequality 3, it is easy to forget to change the direction of the invariant sign, which leads to the wrong result.

4. The topic of the range of the quadratic equation in one variable is easily ignored, and the coefficient of the quadratic term is not 0.

Second, rational numbers.

1, addition of rational numbers

Two numbers with the same sign are added, and the absolute value is added with the same sign.

Different symbols increase or decrease, large numbers determine and symbols.

Add up the opposites of each other, and the result is that zero must be remembered well.

"Big" minus "small" refers to the absolute value.

2. Rational number subtraction

Negative is equal to plus negative, and reducing the burden is equal to plus positive.

Symbolic law of rational number multiplication.

The sign of the same sign is negative and the product of a term is zero.

Representation of Cubic and Quadratic Resolution Functions

1, general formula: y=ax2+bx+c(a, b, c are constants, a≠0), such as y = 2x2+3x+4;

2. Vertex type: y=a(x-h)2+k(a, h, k are constants, a≠0), such as y = 2 (x-5) 2+3;

3. two formulas: y=a(x-x 1)(x-x2)(a≠0, x 1, x2 is the abscissa of the intersection of parabola and x axis), such as y=2(x- 1)(x+3).