The formula is called quadratic radical, and quadratic radical must satisfy: it contains quadratic radical sign; The root sign a must be non-negative.

2. The simplest quadratic radical

If the square root satisfies: the factor of the square root is an integer and the factor is an algebraic expression; The square root number contains no factor or can be completely opened. Such a quadratic root is called the simplest quadratic root.

3. Similar quadratic roots

After several quadratic roots are transformed into the simplest quadratic roots, if the number of roots is the same, these quadratic roots are called similar quadratic roots.

4. Quadratic radical

The formula is called quadratic root, which must meet the following requirements: the number of squares a containing quadratic roots must be non-negative.

5. The simplest quadratic root

If the square root satisfies: the factor of the square root is an integer and the factor is an algebraic expression; The square root number contains no factor or can be completely opened. Such a quadratic root is called the simplest quadratic root.