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If the point of intersection of the lines `2px+3qy+r=0` and `px-2qy-2r=0` lies strictly in the fourth quadrant and is equidistant from the two axes, then

A

`5p+4q=0`

B

`4p-5q=0`

C

`4p+5q=0`

D

`5p-4q=0`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the conditions under which the point of intersection of the lines \(2px + 3qy + r = 0\) and \(px - 2qy - 2r = 0\) lies strictly in the fourth quadrant and is equidistant from the two axes. ### Step 1: Find the point of intersection of the two lines. To find the point of intersection, we can solve the two equations simultaneously. 1. The first equation is: \[ 2px + 3qy + r = 0 \quad \text{(1)} \] 2. The second equation is: \[ px - 2qy - 2r = 0 \quad \text{(2)} \] We can express \(y\) from equation (1): \[ 3qy = -2px - r \implies y = \frac{-2px - r}{3q} \quad \text{(3)} \] Now substitute equation (3) into equation (2): \[ px - 2q\left(\frac{-2px - r}{3q}\right) - 2r = 0 \] ### Step 2: Simplify the equation. Substituting and simplifying: \[ px + \frac{4px + 2r}{3} - 2r = 0 \] Multiply through by 3 to eliminate the fraction: \[ 3px + 4px + 2r - 6r = 0 \] Combine like terms: \[ 7px - 4r = 0 \implies 7px = 4r \implies x = \frac{4r}{7p} \quad \text{(4)} \] ### Step 3: Substitute \(x\) back to find \(y\). Now substitute \(x\) from equation (4) back into equation (3): \[ y = \frac{-2p\left(\frac{4r}{7p}\right) - r}{3q} = \frac{-\frac{8r}{7} - r}{3q} = \frac{-\frac{8r + 7r}{7}}{3q} = \frac{-\frac{15r}{7}}{3q} = \frac{-5r}{7q} \quad \text{(5)} \] ### Step 4: Analyze the coordinates. Now we have the coordinates of the intersection point: \[ \left( \frac{4r}{7p}, \frac{-5r}{7q} \right) \] For the point to lie in the fourth quadrant: - \(x > 0\) implies \(r > 0\) (since \(p\) is a constant and must not be zero). - \(y < 0\) implies \(q > 0\) (since \(r\) is positive). ### Step 5: Condition of equidistance from the axes. The point is equidistant from the axes if: \[ \left| \frac{4r}{7p} \right| = \left| \frac{-5r}{7q} \right| \] Since both \(r\) and \(p\) are positive, we can drop the absolute values: \[ \frac{4r}{7p} = \frac{5r}{7q} \] Cancelling \(r\) (since \(r \neq 0\)): \[ \frac{4}{p} = \frac{5}{q} \implies 4q = 5p \implies 5p - 4q = 0 \] ### Conclusion Thus, the final condition that satisfies the problem is: \[ 5p - 4q = 0 \]
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