The common formula of factorization is 1, and the square difference formula is: a? -B? =(a+b)(a-b).
2. Complete square formula: a? +2ab+b？ =(a+b)？ .
3. Cubic sum formula: A? +b？ =(a+b)(a？ -ab+b？ )。
4. Cubic difference formula: a? -B? =(a-b)(a？ +ab+b？ )。
5. Complete cubic sum formula: a? +3a？ b+3ab？ +b？ =(a+b)？ .
6. Complete cubic difference formula: a? -3a？ b+3ab？ -B? =(a-b)？ .
7. Three complete square formulas: A? +b？ +c？ +2ab+2bc+2ac=(a+b+c)？ .
8. the formula of cubic sum of three terms: a? +b？ +c？ -3abc=(a+b+c)(a？ +b？ +c？ -ab-bc-ac).
The number in the root sign of the square root formula can be changed to the same or the same, so it can be added or subtracted, and different ones cannot be added or subtracted.
If the numbers in the root sign are the same, they can be added or subtracted; If the numbers in the root sign are different, you can't add or subtract; If you can simplify it to numbers with the same root sign, you can add and subtract.
Examples are as follows:
(1)2√2+3√2=5√2 (all the numbers in the root sign are 2 and can be added).
(2)2√3+3√2 (one of the radicals is 3 and the other is 2, which cannot be added)
(3)√5+√20=√5+2√5=3√5 (although the numbers in the radical symbols are different, they can be replaced by the same ones and added).
(4)3√2-2√2=√2
(5)√20-√5=2√5-√5=√5
Multiplication and division of root sign:
√ AB = √ A √ B (A ≥ 0B ≥ 0), for example: √ 8 = √ 4 √ 2 = 2 √ 2.
√a/b=√a÷√b
Trigonometric inequality | A+B |≤| A |+B|
|a-b|≤|a|+|b|
| a |≤b & lt； = & gt-b≤a≤b
|a-b|≥|a|-|b|
-|a|≤a≤|a|
Rectangular common graphic area formula = length× width S = ab
Area of a square = side length × side length S = a?
Area of triangle = base × height ÷2 S=ah÷2.
Area of parallelogram = base × height S=ah
Trapezoidal area = (upper bottom+lower bottom) × height ÷2 S=(a+b)h÷2.
Area of circle = π× radius× radius
Multiplication and factorization of equations;
a2-b2=(a+b)(a-b)
a3+b3=(a+b)(a2-ab+b2)
a3-b3=(a-b)(a2+ab+b2)
Solution of quadratic equation in one variable;
-b+√(B2-4ac)/2a-b-b+√(B2-4ac)/2a