For example, the square of 2 is 4, the square of 3 is 9, the cube of 2 is 8 and the cube of 3 is 27. Then reverse the operation, 4 roots are 2 (square root, positive number), 9 roots are 3, 8 roots are 2, and 27 roots are 3.

The origin of the name of the formula: Zhou Bi Zhao's note on the Pythagorean Square Map: "Pythagoras shares are multiplied separately to form a chord, and the formula is divided into chords." The squares of the two sides of a right triangle are added, and the square of the third side is the square of the right triangle.

Extended data properties:

In the range of real numbers, any real number has only one odd root, for example, the cube root of 8 is 2 and the cube root of -8 is -2.

Even roots of positive real numbers are two numbers with opposite directions, for example, the fourth roots of 16 are 2 and -2.

Negative real numbers have no even roots; Any power root of zero is zero.