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AlgebraVery hardIntercept in terms of a parameter

Algebra practice question

The graph of a linear function f has slope 2 and passes through the point (k, k), where k is a nonzero constant. Which expression gives f(0)?

  1. A. −kCorrect
  2. B. k
  3. C. 2k
  4. D. −2k

Answer: A. −k

f(x) = 2(x − k) + k = 2x − k, so f(0) = −k.

Why the other answers are wrong

B. k
k is f(k), the given value, not f(0).
C. 2k
2k is the change from x = 0 to x = k, not the intercept.
D. −2k
−2k double-counts the slope term.

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