Square root formula: negative square root is no good, zero square root is still zero. There are two positive square roots with opposite signs and the same value. The root finger can be omitted, and the rest must be made clear. Negative numbers have only odd roots, and the arithmetic square root is zero or positive.

The square root of 1 to 20: 1? = 1 ,2? =4,3? =9,4? = 16,5? =25,6? =36,7? =49,8? =64,9? =8 1, 10? = 100, 1 1? = 12 1, 12? = 144, 13? = 169, 14? = 196, 15? =225 , 16? =256, 17? =289, 18? =324, 19? =36 1,20? =400。

Square root formula: 1 1- 19 square: original number plus mantissa, mantissa square; Every 10 decimal; Square of 4 1-49: at the end, add 15, subtract 10 and square it again, accounting for 2 digits; The square of 5 1-59: the tail is added with 25, and the tail square takes 2 places; Square of 965438 +0-99: mantissa multiplied by 2 plus 80, 10 minus mantissa and then squared, accounting for 2 digits.

Extended data:

If a positive number has a square root, then there must be two, and it is reciprocal. Obviously, if we know one of these two square roots, we can get the other square root in time according to the concept of reciprocal.

In a real number system, negative numbers cannot be squared. Only in a complex system can negative numbers be squared. The square root of a negative number is the pure imaginary number of a pair of yokes. For example, the square root of-1 is I, and the square root of -9 is 3i, where I is an imaginary unit.