Function notation, step by step
f(4) is a name for a value, not f times 4.
The question
Find f(−4).
f(x) = 2x + 11; f(−4)
f(x) = 2x + 11atx = −4
2 × (−4)=−8
−8+11=3
f(−4)=3
- f(−4) is a name for the value of the rule when x = −4. Put −4 where the x is — it is not f times −4.
- Multiply first, sign and all: 2 × (−4) = −8.
- Then add 11: −8 + 11 = 3.
- So f(−4) = 3.
How it works.
- 01
f(−4) is a name for the value of the rule when x = −4. Put −4 where the x is — it is not f times −4.
- 02
Multiply first, sign and all: 2 × (−4) = −8.
- 03
Then add 11: −8 + 11 = 3.
- 04
So f(−4) = 3.