If the square of a number is equal to A, then this number is called the square root or quadratic root of A. If x2=a, then X is called the square root of A, and A is called the square root.

2. Representation of square root: the square root of a positive number is expressed as "a?" , pronounced "positive and negative root a". 3. The nature of the square root:

(1) Positive numbers have two square roots, and the two square roots are in opposite directions. (2) The square root of 0 is 0. (3) Negative numbers have no square roots.

4. square root: the operation of finding the square root of a number is called square root, where a is called square root. 5. Note:

(1) A is a non-negative number (that is, positive number or 0)(a≥0) (2) The sum of squares and the square root are reciprocal operations.

(3) A positive number has two square roots, and the two square roots are in opposite directions. Never lose the negative square root. (4) Finding the square root of a number is just the opposite of finding the square of a number. Second, the arithmetic square root.

1. the concept of arithmetic square root: if the square of a positive number x is equal to a, that is, x2 = a(x >；); 0), then this positive number x is called the arithmetic square root of a.

2. Representation method of arithmetic square root: the arithmetic square root of A is recorded as the arithmetic square root of A, and the arithmetic square root of 3.0 is read as "root number A", which is 0. Negative numbers have no arithmetic square root.