# Find the value of x for which the points(x, -1), (2, 1) and (4, 5) are collinear.

Let the points be A(x, -1), B(2, 1) and C(4, 5)

Now as the points are collinear, therefore

mAB = MBC

Now mAB = = and mBC = = = 2

As mAB = mBC

We have = 2

2 = 2(2 – x) = 4 – 2x

or 2x = 4 – 2

⇒ 2x = 2 ⇒ x = 1

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