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Mathematics

The value of m such that the points A(5, –2), B(8, –3) and C(m, –12) are collinear, is:

  1. 29

  2. 33

  3. 35

  4. 41

Straight Line Eq

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Answer

For three points A, B, and C to be collinear.

mAB = mBC

We know that,

m = y2y1x2x1\dfrac{y2 - y1}{x2 - x1}

Using A(5, -2) and B(8, -3) :

mAB=3(2)85=13.m_{AB} = \dfrac{-3 - (-2)}{8 - 5} \\[1em] = \dfrac{-1}{3}.

Using B(8, -3) and C(m, -12):

mBC=12(3)m8=9m8m_{BC} = \dfrac{-12 - (-3)}{m - 8} \\[1em] = \dfrac{-9}{m - 8}

mAB = mBC

13=9m8\dfrac{-1}{3} = \dfrac{-9}{m - 8}

⇒ -1(m - 8) = -9 × 3

⇒ -m + 8 = -27

⇒ -m = -27 - 8

⇒ -m = -35

⇒ m = 35.

Hence, option 3 is the correct option.

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