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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