Question:

A straight line through the origin O meets the parallel lines $4x + 2y = 9 $ and $2x + y + 6 = 0$ at points P and Q respectively. Then, the point O divides the segment PQ in the ratio

Updated On: Aug 24, 2023
  • 1:2

  • 3:4

  • 2:1

  • 4:3

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The Correct Option is B

Solution and Explanation

The correct answer is B:\(3\ratio4\)
Given that;
The equation of the line is:-
\(4x+2y=9-(i)\) and \(2x+y=-6-(ii)\)
Let the equation of the line passes through the origin: \(y=mx-(iii)\)
Then two intersection of (i) and (iii)
\(x_1=\frac{9}{4+2m},y=\frac{9m}{4+2m}|p(\frac{9}{4+2m},\frac{9m}{4+2m})\)
similarly, (ii) and (iii);
\(x_2=\frac{-6}{2+m},y_2=\frac{-6m}{2+m}|q(\frac{-6}{2+m},\frac{-6m}{2+m})\)
Let us consider a point ‘O’ denotes PQ in the ratio of \(1\ratio{K}\)
\(\therefore 0=\frac{K(\frac{9}{4+2m}-\frac{6}{2+m})}{K+m}\) and \(\frac{K(\frac{9m}{4+2m}-\frac{6m}{2+1})}{K+1}\)
\(K=\frac{6\times2}{9}=\frac{4}{3}\)
\(\therefore K=\frac{4}{3}\)   \(\therefore Ratio\space is \space3\ratio{4}\)
Equation of line
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Questions Asked in JEE Advanced exam

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Concepts Used:

Straight lines

A straight line is a line having the shortest distance between two points. 

A straight line can be represented as an equation in various forms,  as show in the image below:

 

The following are the many forms of the equation of the line that are presented in straight line-

1. Slope – Point Form

Assume P0(x0, y0) is a fixed point on a non-vertical line L with m as its slope. If P (x, y) is an arbitrary point on L, then the point (x, y) lies on the line with slope m through the fixed point (x0, y0) if and only if its coordinates fulfil the equation below.

y – y0 = m (x – x0)

2. Two – Point Form

Let's look at the line. L crosses between two places. P1(x1, y1) and P2(x2, y2)  are general points on L, while P (x, y) is a general point on L. As a result, the three points P1, P2, and P are collinear, and it becomes

The slope of P2P = The slope of P1P2 , i.e.

\(\frac{y-y_1}{x-x_1} = \frac{y_2-y_1}{x_2-x_1}\)

Hence, the equation becomes:

y - y1 =\( \frac{y_2-y_1}{x_2-x_1} (x-x1)\)

3. Slope-Intercept Form

Assume that a line L with slope m intersects the y-axis at a distance c from the origin, and that the distance c is referred to as the line L's y-intercept. As a result, the coordinates of the spot on the y-axis where the line intersects are (0, c). As a result, the slope of the line L is m, and it passes through a fixed point (0, c). The equation of the line L thus obtained from the slope – point form is given by

y – c =m( x - 0 )

As a result, the point (x, y) on the line with slope m and y-intercept c lies on the line, if and only if

y = m x +c