Q11 of 23 Page 330

If (0, 0), (4, –3) and (x, y) are collinear then

Let A = (0, 0), B = (4, -3) and C = (x, y)


As the points are collinear area of triangle formed by these points is 0


Area = × [x1(y2 – y3) + x2(y3 – y1) + x3(y1 – y2)]


Where (x1, y1), (x2, y2) and (x3, y3) are vertices of triangle


Here,


(x1, y1) = (0, 0)


(x2, y2) = (4, -3)


(x3, y3) = (x, y)


Substituting values


0 = × [0(-3 – y) + 4(y – 0) + x(0 – (-3))]


0 = 0 + 4y + 3x


4y + 3x = 0


Here there are infinite values for x and y which will satisfy the equation 4y + 3x = 0 which means there are infinite points


This can also be seen geometrically that is if line is passing through (0, 0) and (4, -3) there are infinite points on this line.


We can select the correct option by substituting the values given in option in equation 4y + 3x = 0 and if it satisfies then that is the correct option


x = 8, y = -6 satisfies the equation 4y + 3x = 0


x = –8, y = 6 satisfies the equation 4y + 3x = 0


Now, C = (8, -6) or C = (-8, 6), but for A, B and C to be collinear


AB + BC = AC
We know, By distance formula, Distance between two points X(x1, y1) and Y(x2, y2) is



Case I: C = (8, -6)


AB


units


BC


units


AC


units


Clearly, AB + BC = AC


Hence, (0, 0), (4, -3) and (8, -6) are collinear


Case II: C = (-8, 6)


AB


units


BC


units


AC


units


Clearly, AB + BC ≠ AC


Hence, (0, 0), (4, -3) and (8, -6) are not collinear.


[In this case, BA + AC = BC, B, A and C are collinear]


Hence, Correct option is (a)

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