If the midpoint of the line joining (1 - k, -4) and (2, k +
FURTHER MATHEMATICS
WAEC 2012
If the midpoint of the line joining (1 - k, -4) and (2, k + 1) is (-k, k), find the value of k.
- A. -4
- B. -3
- C. -2
- D. -1
Correct Answer: D. -1
Explanation
Midpoint between \((x_{1}, y_{1})\) and \((x_{2}, y_{2})\) = \((\frac{x_{1} + x_{2}}{2}, \frac{y_{1} + y_{2}}{2})\).
\((-k, k) = (\frac{2 + (1 + k)}{2}, \frac{-4 + (k + 1)}{2})\)
\(-k = \frac{k + 3}{2} \implies -2k = k + 3\)
\(-3k = 3 \implies k = -1\)
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