AlgebraEasy–MediumFunction from a slope and one value
Algebra practice question
A linear function f has a slope of 3, and f(2) = 5. Which equation defines f?
- A. f(x) = 3x − 1Correct
- B. f(x) = 3x + 5
- C. f(x) = 3x + 2
- D. f(x) = 2x + 3
Answer: A. f(x) = 3x − 1
f(x) = 3x + b. From f(2) = 5: 6 + b = 5, so b = −1. f(x) = 3x − 1.
Why the other answers are wrong
- B. f(x) = 3x + 5
- 3x + 5 uses the given value 5 as the intercept; but f(2) = 11 then, not 5.
- C. f(x) = 3x + 2
- 3x + 2 uses the input 2 as the intercept; f(2) would be 8.
- D. f(x) = 2x + 3
- 2x + 3 has slope 2, but the slope is 3.
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