Overview
Evaluating a function means finding the output f(x) for a given input x. The process is simple: substitute x into the expression and compute the result using the order of operations. The expression may be linear, quadratic, or include roots and trigonometric functions.
Formula
If f(x) = an expression, then f(a) is the result after replacing every x with the number a.
How it works
Write the function expression
Use x, arithmetic operators and supported functions.
Choose the x value
Enter the value at which to evaluate the function.
Substitute and compute
Replace x with the value and apply the order of operations.
Read the result
f(x) appears along with extra values at 0, 1 and −1.
Worked examples
Example 1: f(x) = 2x² + 3x − 1 at x = 2
f(2) = 8 + 6 − 1 = 13.
Example 2: f(x) = √(x + 4) at x = 5
f(5) = √9 = 3.
Frequently asked questions
Which functions are supported?
Roots, logarithms, trigonometric and exponential functions such as sqrt, ln, sin, cos and exp.
What if the value is outside the domain?
An error appears because the function is undefined at that value.
Can I use a variable other than x?
The calculator is designed for x, so write expressions using x only.
This calculator is for educational and informational purposes only and is not a substitute for professional advice.