Evaluating f(a) means: drop a in for x, simplify.
Try this
3
f(x) = 2x² − 3x + 1 = 10
How to evaluate f(a)
- Wherever you see x in the rule, write (a) — with brackets.
- Simplify using order of operations: powers before multiplication before addition.
- The result is one number: the output of the function at that input.
Your turn
If f(x) = x² − 4x, find f(−2).
Brackets matter: f(x) = −x² at x = 3 is −(3²) = −9, not (−3)² = 9. Substitute the input inside parentheses every time.
Try it
f(x) = 2x² + 1, find f(3)
2(9) + 1 = 19.