How to answer it
- Evaluate each function value separately.
- Keep negative results in parentheses.
- Then combine as the question asks.
Worked example
An original question in the ACT format, already answered.
ACT MathWorked example
g(x) = x² − 4x
What is the value of g(5) − g(1)?
- A2
- B4
- C8
- D12
Answer: C. g(5) = 25 − 20 = 5 and g(1) = 1 − 4 = −3. Then 5 − (−3) = 8. Choice A subtracts 3 instead of −3.
The most common trap
Losing a negative sign when subtracting a negative value.
Practice it
Hourly Prep’s daily sets mix functions with the rest of ACT Math, and send more of it your way when it’s a weak spot. See how the ACT prep plan works, or browse the other ACT skill guides.