Question:

Suppose \(P\) and \(Q\) lie on \[ 3x+4y-4=0 \] and \[ 5x-y-4=0 \] respectively. If the midpoint of \(PQ\) is \((1,5)\), then the slope of the line passing through \(P\) and \(Q\) is

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When midpoint is given, write the second point in terms of the first point using midpoint formula, then substitute into the given line equations.
Updated On: Jun 22, 2026
  • \(\frac{83}{35}\)
  • \(\frac{63}{35}\)
  • \(-\frac34\)
  • \(\frac34\)
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The Correct Option is A

Solution and Explanation

Step 1: Let coordinates of \(P\) and \(Q\).
Let \[ P=(x_1,y_1) \] and \[ Q=(x_2,y_2) \] Since midpoint is \((1,5)\), \[ \frac{x_1+x_2}{2}=1 \] and \[ \frac{y_1+y_2}{2}=5 \] So, \[ x_1+x_2=2 \] and \[ y_1+y_2=10 \]

Step 2: Express \(Q\) in terms of \(P\).
\[ x_2=2-x_1 \] and \[ y_2=10-y_1 \]

Step 3: Use line equations.
Since \(P\) lies on \[ 3x+4y-4=0, \] we get \[ 3x_1+4y_1=4 \] Since \(Q\) lies on \[ 5x-y-4=0, \] we get \[ 5x_2-y_2=4 \] Substitute \(x_2=2-x_1\) and \(y_2=10-y_1\): \[ 5(2-x_1)-(10-y_1)=4 \] \[ 10-5x_1-10+y_1=4 \] \[ y_1-5x_1=4 \]

Step 4: Solve for \(P\).
We have \[ 3x_1+4y_1=4 \] and \[ y_1-5x_1=4 \] From second equation, \[ y_1=5x_1+4 \] Substitute in first equation: \[ 3x_1+4(5x_1+4)=4 \] \[ 3x_1+20x_1+16=4 \] \[ 23x_1=-12 \] \[ x_1=-\frac{12}{23} \] Then, \[ y_1=5\left(-\frac{12}{23}\right)+4 \] \[ y_1=\frac{32}{23} \]

Step 5: Find \(Q\).
\[ x_2=2-x_1=2+\frac{12}{23} \] \[ x_2=\frac{58}{23} \] \[ y_2=10-y_1=10-\frac{32}{23} \] \[ y_2=\frac{198}{23} \]

Step 6: Find slope of \(PQ\).
\[ m=\frac{y_2-y_1}{x_2-x_1} \] \[ m= \frac{\frac{198}{23}-\frac{32}{23}}{\frac{58}{23}+\frac{12}{23}} \] \[ m=\frac{\frac{166}{23}}{\frac{70}{23}} \] \[ m=\frac{166}{70} \] \[ m=\frac{83}{35} \] Therefore, \[ \boxed{\frac{83}{35}} \]
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