Question:

The equations of the pairs of opposite sides of a parallelogram are \[ x^2-5x+6=0 \] and \[ y^2-6y+5=0. \] Then the equations of its diagonals are

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When quadratic equations split into pairs of lines, first factorize them completely. The intersection points of those lines give the vertices of the required figure.
Updated On: Jun 17, 2026
  • \(4x-y-7=0,\;4x+y=13\)
  • \(4x+y-7=0,\;4x-y=13\)
  • \(4x-y-7=0,\;x+4y=13\)
  • \(4x+y+7=0,\;x-4y=13\)
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The Correct Option is A

Solution and Explanation

Concept: The equations \[ x^2-5x+6=0 \] and \[ y^2-6y+5=0 \] represent pairs of parallel lines. Their intersections form the vertices of a parallelogram. The diagonals join opposite vertices.

Step 1: Factorize the equations.
First equation: \[ x^2-5x+6=0 \] gives \[ (x-2)(x-3)=0. \] Hence the pair of lines are \[ x=2,\qquad x=3. \] Second equation: \[ y^2-6y+5=0 \] gives \[ (y-1)(y-5)=0. \] Hence the pair of lines are \[ y=1,\qquad y=5. \]

Step 2: Find vertices of parallelogram.
The vertices are intersections: \[ (2,1),\;(2,5),\;(3,1),\;(3,5). \]

Step 3: Find equations of diagonals.
One diagonal joins \((2,1)\) and \((3,5)\). Slope: \[ m=\frac{5-1}{3-2}=4. \] Equation: \[ y-1=4(x-2). \] Thus, \[ y-1=4x-8 \] which gives \[ 4x-y-7=0. \] Second diagonal joins \((2,5)\) and \((3,1)\). Slope: \[ m=\frac{1-5}{3-2}=-4. \] Equation: \[ y-5=-4(x-2). \] Hence, \[ y-5=-4x+8 \] which simplifies to \[ 4x+y=13. \] Therefore the diagonals are \[ \boxed{4x-y-7=0,\;4x+y=13}. \]
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