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The Square Root

The square root is the reverse operation of squaring a number.

Example 1.

32 = 9,  so 3 is a square root of 9.

(-3)2 = 9,  so -3 is also a square root of 9.



  = , so is a square root of
  = , so is also a square root of


Since r2 = -1 has no real number solution, -1 does not have a real square root.

  • More generally, since b2 ≥ 0 for any real number b, negative numbers have no real square root.
  • Any positive number has two square roots.
  • The number 0 has only one square root; namely 0.

For any positive number b, the positive square root is denoted bysqrt(b) and the negative square root is denoted by -sqrt(b) .


The graph of x2 is shown below. You can see that for any positive number b, there exists a positive and a negative root.

The graph of x^2 is a parabola with vertex at the origin.

When writing the two square roots of a positive number b, we combine the two roots as + or - sqrt(b). .

For example, the square roots of 4 are + or - sqrt(4) = + or - 2 and the square roots of 1 are + or - sqrt(1) = + or - 1 .

Not all square roots of a number are integers. For example, sqrt(2) and sqrt(3) are not integers.


If the square root of b exists and is an integer write it in the box then check it. If the square root exists but is not an integer, click on "Real Root is Not Integer". If the number b does not have a real square root, click on "No Real Root".

b =


square root of b  =  ±     for an integer root.

Exponents Index | Cube Root >>


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