Prove that the area of the parallelogram formed by the lines 3x – 4y + a = 0, 3x –4y + 3a = 0, 4x – 3y – a = 0 and 4x – 3y – 2a = 0 is 2a2/7 sq. units.
Prove that the area of the parallelogram formed by the lines 3x – 4y + a = 0, 3x –4y + 3a = 0, 4x – 3y – a = 0 and 4x – 3y – 2a = 0 is 2a2/7 sq. units.

The given lines are

    \[\begin{array}{*{35}{l}} 3x~-~4y\text{ }+\text{ }a\text{ }=\text{ }0\text{ }\ldots \text{ }\left( 1 \right)  \\ 3x~-~4y\text{ }+\text{ }3a\text{ }=\text{ }0\text{ }\ldots \text{ }\left( 2 \right)  \\ 4x~-~3y~-~a\text{ }=\text{ }0\text{ }\ldots \text{ }\left( 3 \right)  \\ 4x~-~3y~-~2a\text{ }=\text{ }0\text{ }\ldots \text{ }\left( 4 \right)  \\ \end{array}\]

Let us prove, the area of the parallelogram formed by the lines 3x – 4y + a = 0, 3x – 4y + 3a = 0, 4x – 3y – a = 0 and 4x – 3y – 2a = 0 is 2a2/7 sq. units.

From above solution, we know that

RD Sharma Solutions for Class 11 Maths Chapter 23 – The Straight Lines - image 91

Hence proved.