AlgebraMediumValue of a linear function from its slope and one value
Algebra practice question
The graph of the linear function f has slope 1/4, and f(8) = 5. What is the value of f(−4)?
Answer: 2
From x = 8 to x = −4 is a change of −12 in x, so f changes by (1/4)(−12) = −3: f(−4) = 5 − 3 = 2.
Common wrong answers
- If you answered 4
- 4 comes from 5 − (1/4)(4), using −4 as the change in x.
- If you answered 8
- 8 adds 3 instead of subtracting.
- If you answered -1
- −1 comes from 5 − (1/4)(24), doubling the change in x.
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