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Evaluating Functions
Work out f(a) by substituting a for x in the function's rule.
Substituting into a Function
Evaluating a function works exactly like substitution from the algebra course: replace every with the given input, then simplify using BODMAS.
Example 1 — easy numbers
f() = . Find f().
- Replace with : f() = () +
- Multiply: () =
- Add:
Answer: f() =
Example 2 — negative input
f() = . Find f.
- Replace with : f² −
- Work out each part: ² = , and , so
- Add:
Answer: f
Example 3 — solving for the input
f() = . Find the value of for which f() = .
- Set up the equation:
- Subtract :
- Divide by :
Answer:
Practice
() = . Find ().
Your answer
More lessons in Sets and Functions · Next: Composite Functions · Previous: Domain and Range