AlgebraMediumLinear function from a difference and an intercept
Algebra practice question
For the linear function f(x) = mx + b, f(3) − f(1) = 8 and f(0) = −1. What is the value of f(5)?
Answer: 19
f(3) − f(1) = 2m = 8, so m = 4, and b = f(0) = −1. Then f(5) = 4(5) − 1 = 19.
Common wrong answers
- If you answered 20
- 20 is 4 × 5, forgetting the intercept.
- If you answered 21
- 21 uses b = +1.
- If you answered 39
- 39 uses m = 8, forgetting that 8 is the change over 2 units.
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