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Mathematics

Assertion (A): The point P(3, -1) divides the line segment joining the points A(1, -3) and B(6, 2) internally in the ratio 2 : 3.

Reason (R): The coordinates of the point which divides the line segment joining the points A(x1, y1) and B(x2, y2) internally in the ratio m1 : m2 are (m1x2+m2x1m1+m2,m1y2+m2y1m1+m2)\Big(\dfrac{m1x2 + m2x1}{m1 + m2}, \dfrac{m1y2 + m2y1}{m1 + m2}\Big).

  1. Assertion (A) is true, Reason (R) is false.

  2. Assertion (A) is false, Reason (R) is true.

  3. Both Assertion (A) and Reason (R) are correct, and Reason (R) is the correct reason for Assertion (A).

  4. Both Assertion (A) and Reason (R) are correct, and Reason (R) is incorrect reason for Assertion (A).

Section Formula

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Answer

By section-formula,

The coordinates of the point which divides the line segment joining the points A(x1, y1) and B(x2, y2) internally in the ratio m1 : m2 are

(m1x2+m2x1m1+m2,m1y2+m2y1m1+m2)\Big(\dfrac{m1x2 + m2x1}{m1 + m2}, \dfrac{m1y2 + m2y1}{m1 + m2}\Big).

So, reason (R) is true.

Let us find the point P which divides the line segment joining A(1, -3) and B(6, 2) in the ratio 2 : 3, by section-formula.

P=(2×6+3×12+3,2×2+3×(3)2+3)=(12+35,495)=(155,55)=(3,1)\Rightarrow \text{P} = \Big(\dfrac{2 \times 6 + 3 \times 1}{2 + 3}, \dfrac{2 \times 2 + 3 \times (-3)}{2 + 3}\Big)\\[1em] = \Big(\dfrac{12 + 3}{5}, \dfrac{4 - 9}{5}\Big)\\[1em] = \Big(\dfrac{15}{5}, \dfrac{-5}{5}\Big)\\[1em] = (3, -1)

So, assertion (A) is true.

Thus, both A and R are correct, and R clearly explains A.

Hence, option 3 is the correct option.

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