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Question
If (x , 2), (−3, −4) and (7, −5) are collinear, then x =
Options
60
63
−63
−60
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Solution
We have three collinear points A (x , 2 ) ; B ( -3 ,-4) ; C(7 , - 5).
In general if A (x1 , y1) ; B (x2 , y2) ; C (x3 , y 3). are collinear then,
`x_1 ( y_2 -y_3) + x_2 (y_3 - y_1) + x_3 (y_1 - y_2 ) = 0`
So,
x (-4 + 5 ) -3 (-5-2)+ 7 (2 +4) = 0
So,
`x + 42 + 21 = 0`
Therefore,
x = - 63
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