Algebra practice question

Answer: 4

Slope is the change in y over the change in x: (−2 − 4)/(2 − k) = 3. So −6 = 3(2 − k), giving −6 = 6 − 3k, then −12 = −3k and k = 4. Check: (−2 − 4)/(2 − 4) = −6/−2 = 3.

Common wrong answers

If you answered 0

0 comes from −6 = 3(2 − k) solved as 2 − k = 2. Dividing −6 by 3 gives −2, so 2 − k = −2 and k = 4.

If you answered 8

8 would come from using (4 − (−2))/(k − 2) = 3 as 6 = 3k − 2 — the 2 must be multiplied by 3 too: 6 = 3k − 6, so k = 4.

If you answered −4

−4 is a sign error at the last step: −12 = −3k gives k = +4.

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