Question

(b) The co-ordinates of three points are A(7, 4), B(-1, -2) and C(3t, 5-4t). (i) Find the value of t if the three points are collinear.​

Answer 1

6/7

Explanation:

If the three points are collinear, then the slope of the line passing through any two of the points should be the same as the slope of the line passing through the other two points.

Let's find the slope of the line passing through points A and B:

slope AB = (y2-y1)/(x2-x1)

= (-2-4)/(-1-7)

= -6/-8

= 3/4

Now let's find the slope of the line passing through points B and C:

slope BC = (y2-y1)/(x2-x1)

= (5-4t-(-2))/(3t-(-1))

= (7-4t)/(3t+1)

Since the three points are collinear, slope AB = slope BC:

3/4 = (7-4t)/(3t+1)

Cross-multiplying and simplifying:

12t + 4 = 28-16t

28t = 24

t = 24/28

t = 6/7

Therefore, the value of t is 6/7 if the three points A, B, and C are collinear.

Answer 2

Explanation:

To determine the value of t if the three points A(7, 4), B(-1, -2), and C(3t, 5-4t) are collinear, we can use the concept of slope. If the points are collinear, the slopes between any two pairs of points should be equal.

The slope between points A and B is given by:

m₁ = (y₂ - y₁) / (x₂ - x₁)

= (-2 - 4) / (-1 - 7)

= (-6) / (-8)

= 3/4

Now, let's calculate the slope between points B and C:

m₂ = (y₂ - y₁) / (x₂ - x₁)

= (5 - (-2)) / (3t - (-1))

= (7) / (3t + 1)

Since the points are collinear, the slopes m₁ and m₂ should be equal. Therefore, we can set up the equation:

3/4 = 7 / (3t + 1)

To solve for t, we can cross-multiply and solve the resulting equation:

4(7) = 3(3t + 1)

28 = 9t + 3

25 = 9t

t = 25 / 9

Therefore, the value of t that makes the points A(7, 4), B(-1, -2), and C(3t, 5-4t) collinear is t = 25/9.