Collinear points and a line that avoids y = 2x

Collinear points and a line that avoids y = 2x

IP 1
7 marks

The points \(A(-2,-1)\), \(B(1,5)\) and \(C(4,11)\) are given.

  1. By finding the gradients of \(AB\) and \(BC\), show that \(A\), \(B\) and \(C\) lie on one straight line, and find the equation of this line.[3]
  2. Explain why no point of the form \((k,2k)\) lies on this line.[2]
  3. Find the point on the line whose \(y\)-coordinate is three times its \(x\)-coordinate.[2]

Solution:

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Answer:(a) \(m_{AB}=m_{BC}=2\) with common point \(B\); \(y=2x+3\) (b) \(2k=2k+3\) gives \(0=3\): \(y=2x\) is parallel to the line (c) \((3,9)\)

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