Algebra practice question

Answer: A. f(x) = 2x + 3

Slope: (11 − 5)/(4 − 1) = 2. Then 5 = 2(1) + b gives b = 3: f(x) = 2x + 3.

Why the other answers are wrong

B. f(x) = 2x + 5

2x + 5 uses f(1) as the intercept; f(1) is the value at x = 1, not at x = 0.

C. f(x) = 3x + 2

3x + 2 swaps slope and intercept (3(4) + 2 = 14 ≠ 11).

D. f(x) = 6x − 1

6x − 1 uses the change in f (6) as the slope without dividing by the change in x.

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