Radical Functions

Definition: A radical function is a function in which the independent variable is in the radicand (under the radical (√) symbol):

Many people mistakenly call this a ‘square root’ symbol, and many times it is used to determine the square root of a number. However, it can also be used to describe a cube root, a fourth root or higher.


Parent graph of a square-root function:


Parent graph of a cube-root function:



Example: Find the domain: f(x) = √(x – 4)


Because we can only take the square root of values greater than or equal to 0, x – 4 must be greater than or equal to 0.

x – 4 ≥ 0

x ≥ 4

The domain must be all values of x greater than or equal to 4 in order for us to be able to take the square root.

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