Evaluate f(x) = mx + b

What this lesson shows

f(x) = 3x + 2. Evaluate it at 0, at 1, and at 2. One machine… three inputs. Same moves every time.

Try it yourself

Real questions from this lesson's worksheets — answers below each one.

1. Theo computes f(2) for f(x) = 7x + 4 as 7 × (2 + 4) = 42. What went wrong?
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   Theo added 4 before multiplying — multiply 7·2 first, then add 4
2. Theo computes f(3) for f(x) = 6x + 4 as 6 × (3 + 4) = 42. What went wrong?
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   Theo added 4 before multiplying — multiply 6·3 first, then add 4
3. True or false: for f(x) = 3x + 4, f(0) = 7
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   False
4. f(x) = 2x + 1. Find f(2)
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   5