Worked examples
Two examples
Example 1
If f(x) = 2x + 5, what is f(3)?
- f(3) means: put 3 in place of every x.
- 2 × 3 + 5 = 11.
Answer: 11
Example 2
If g(x) = x2 − 4x, what is g(−2)?
- (−2)2 − 4 × (−2) = 4 + 8.
- Square first: (−2)2 is positive 4.
Answer: 12
Where this is taught: Quiz 41: Functions, “What a function is”
The drill
Ten problems
How many:
Type each answer, then press Check my answers at the bottom. Commas in large numbers are fine.Write each answer on the line. The answer key, with the reasoning, is on the last page.