Find a relation between x and y if the points (x, y), (1, 2) and (7, 0) are collinear.

Since, points (x, y), (1.2) and (7,0) are collinear. So area of triangle formed by these points will be zero.
Area of triangle = 1/2[x₁(y₂-y₃)+x₂(y₃-y₁)+x₃(y₁-y₂)]
⇒ Area = 1/2[x(2-0) + 1(0-y)+ 7(y-2)]
⇒ 0 = 1/2[2x-y+7y-14]
⇒ 0 = [2x+6y-14]
⇒ x+3y-7 = 0

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