1, turning a polynomial into the product of several algebraic expressions, this deformation is called decomposing this polynomial.

2. It is a multiplication operation to change the product of several algebraic expressions into polynomial form.

3. Turning a polynomial into the product of several algebraic expressions is factorization.

The same factor contained in each term of a polynomial is called the common factor of each term of this polynomial.

5. Symmetry axis: If a figure is folded along a straight line and the parts on both sides of the straight line can overlap each other, then this figure is called an axisymmetric figure; This straight line is called the axis of symmetry.

6. The essence of isosceles triangle: the two base angles of isosceles triangle are equal.

7. The bisector of the top angle of an isosceles triangle, the height on the bottom edge and the midline on the bottom edge coincide with each other, which is called "three lines in one" for short.

8. Determination of isosceles triangle: equilateral and equilateral.

9. Characteristics of equilateral triangle angles: three internal angles are equal, equal to 60.

10, determination of equilateral triangle: A triangle with three equal angles is an isosceles triangle.

1 1. An isosceles triangle with an angle of 60 is an equilateral triangle.

12. A triangle with two angles of 60 is an equilateral triangle.

13. In a right triangle, the right-angled side facing an angle of 30 is equal to half of the hypotenuse.

14. The midline of the hypotenuse of a right triangle is equal to half of the hypotenuse.