Advanced MathHardComposing a function with itself
Advanced Math practice question
The function f is defined by f(x) = x² + 1. What is the value of f(f(2))?
Answer: 26
Inside first: f(2) = 4 + 1 = 5. Then f(5) = 25 + 1 = 26.
Common wrong answers
- If you answered 5
- 5 is f(2), only the inner step. Apply f once more.
- If you answered 10
- 10 is 2 × f(2), doubling instead of applying f again. Apply f to the result 5: 5² + 1 = 26.
- If you answered 17
- 17 is f(4) = 16 + 1, using 2² = 4 as the inner value instead of f(2) = 5.
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