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Question: Answered & Verified by Expert
If the points $A(5, k), B(-3,1)$ and $C(-7,-2)$ are collinear, then $\mathrm{k}=$
MathematicsStraight LinesMHT CETMHT CET 2020 (15 Oct Shift 1)
Options:
  • A $7$
  • B $\frac{-1}{7}$
  • C $\frac{1}{7}$
  • D $-7$
Solution:
2905 Upvotes Verified Answer
The correct answer is: $7$
Slope of $A B=$ Slope of $B C$
$$
\begin{array}{l}
\frac{1-k}{-3-5}=\frac{-2-1}{-7+3} \Rightarrow \frac{1-k}{-8}=\frac{-3}{-4} \\
\frac{1-k}{2}=-3 \Rightarrow k=7
\end{array}
$$

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