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Question -

Using the method of slopes show that the following points are collinear:
(i) A (4, 8), B (5, 12), C (9, 28)
(ii) A(16, – 18), B(3, – 6), C(– 10, 6)



Answer -

(i) A (4, 8), B (5, 12), C(9, 28)

By using the formula,

The slope of the line= [y2 – y1] / [x2 – x1]

So,

The slope of line AB =[12 – 8] / [5 – 4]

= 4 / 1

The slope of line BC =[28 – 12] / [9 – 5]

= 16 / 4

= 4

The slope of line CA =[8 – 28] / [4 – 9]

= -20 / -5

= 4

Here, AB = BC = CA

The Given points arecollinear.

(ii) A(16, – 18), B(3, –6), C(– 10, 6)

By using the formula,

The slope of the line= [y2 – y1] / [x2 – x1]

So,

The slope of line AB =[-6 – (-18)] / [3 – 16]

= 12 / -13

The slope of line BC =[6 – (-6)] / [-10 – 3]

= 12 / -13

The slope of line CA =[6 – (-18)] / [-10 – 16]

= 12 / -13

= 4

Here, AB = BC = CA

The Given points arecollinear.

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