Question

Determine 'x' if the points (1,5),(2,x) and (-2,-1) are collinear
$sol.7$
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Answer 1

If 3 points A, B and C are collinear then,

Slope of AB = slope of BC = Slope of CA

slope of points (1,5) and (2,x) = slope of points (2,x) and (-2,-1)

(x - 5)/(2-1) = (-1 -x)/(-2-2)

x-5 = (-1-x)/-4

-4x + 20 = -1 -x

3x = 21

x = 7

if the given points are collinear, then x = 7