If the lines 2x – 3y = 5 and 3x – 4y = 7 are the diameters of a circle of area 154square units, then obtain the equation of the circle.
If the lines 2x – 3y = 5 and 3x – 4y = 7 are the diameters of a circle of area 154square units, then obtain the equation of the circle.

Since, diameters of a circle intersect at the centre of a circle,

    \[\begin{array}{*{35}{l}} 2x\text{ }-\text{ }3y\text{ }=\text{ }5\text{ }\ldots \ldots \ldots 1  \\ 3x\text{ }-\text{ }4y\text{ }=\text{ }7\text{ }\ldots \ldots \ldots ..2  \\ \end{array}\]

Solving the above equations,

Multiplying equation 1 by 3 we get

    \[6x\text{ }-\text{ }9y\text{ }=\text{ }15\]

Multiplying equation 2 by 2 we get

    \[\begin{array}{*{35}{l}} 6x\text{ }-\text{ }8y\text{ }=\text{ }14  \\ y\text{ }=\text{ }1  \\ y\text{ }=\text{ }-1  \\ \end{array}\]

Putting y = -1, in equation 1, we get

    \[\begin{array}{*{35}{l}} 2x\text{ }-\text{ }3\left( -1 \right)\text{ }=\text{ }5  \\ 2x\text{ }+\text{ }3\text{ }=\text{ }5  \\ 2x\text{ }=\text{ }2  \\ x\text{ }=\text{ }1  \\ \end{array}\]

Coordinates of centre = (1,-1)

Given area = 154

Area =

    \[\begin{array}{*{35}{l}} \pi {{r}^{2}}~=\text{ }154  \\ 22/7\text{ }\times \text{ }{{r}^{2}}~=\text{ }154  \\ {{r}^{2}}~=\text{ }154\text{ }\times \text{ }7/22  \\ r\text{ }=\text{ }7\text{ }units  \\ \end{array}\]

Since, the equation of a circle having centre (h, k), having radius as r units, is

    \[\begin{array}{*{35}{l}} {{\left( x\text{ }-\text{ }h \right)}^{2}}~+\text{ }{{\left( y\text{ }-\text{ }k \right)}^{2}}~=\text{ }{{r}^{2}}  \\ {{\left( x\text{ }-\text{ }1 \right)}^{2}}~+\text{ }{{\left( y\text{ }\text{ }-\left( -1 \right) \right)}^{2}}~=\text{ }{{7}^{2}}  \\ {{x}^{2}}~\text{ }-2x\text{ }+1\text{ }+\text{ }{{\left( y\text{ }+\text{ }1 \right)}^{2}}~=\text{ }49  \\ {{x}^{2}}~\text{ }-2x\text{ }+\text{ }1\text{ }+\text{ }{{y}^{2}}~+\text{ }2y\text{ }+\text{ }1\text{ }\text{ }-49\text{ }=\text{ }0  \\ {{x}^{2}}~\text{ }-2x\text{ }+\text{ }{{y}^{2}}~+\text{ }2y\text{ }\text{ }-47\text{ }=\text{ }0  \\ \end{array}\]

Hence the required equation of the given circle is x2 – 2x + y2 + 2y – 47 = 0.