Warm Up Solutions

Use the given function to complete problems 1 and 2.

$f (x) = \frac{2}{5} x - \frac{1}{5}$

Evaluate the function at f (5).

$f (5) = \frac{2}{5} (5) - \frac{1}{5} f (5) = 2 - \frac{1}{5} f (5) = 1 \frac{4}{5}$

Note

In this case, it is more efficient to write the answer as a mixed number.

Evaluate the function at f (3a + 1).

$f (3 a + 1) = \frac{2}{5} (3 a + 1) - \frac{1}{5} f (3 a + 1) = \frac{6}{5} a + \frac{2}{5} - \frac{1}{5} f (3 a + 1) = \frac{6}{5} a + \frac{1}{5}$

Note

Q: What will replace x?
A: 3a + 1

Q: How are the answers for problems 1 and 2 different?
A: Sample: Problem 2 has a variable after using substitution, but problem 1 does not.