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,
2x – 3y = 5 ………1
3x – 4y = 7 ………..2
Solving the above equations,
Multiplying equation 1 by 3 we get
6x – 9y = 15
Multiplying equation 2 by 2 we get
6x – 8y = 14
y = 1
y = -1
Putting y = -1, in equation 1, we get
2x – 3(-1) = 5
2x + 3 = 5
2x = 2
x = 1
Coordinates of centre = (1,-1)
Given area = 154
Area = πr2 = 154
22/7 × r2 = 154
r2 = 154 × 7/22
r = 7 units
Since, the equation of a circle having centre (h, k), having radius as r units, is
(x – h)2 + (y – k)2 = r2
(x – 1)2 + (y – (-1))2 = 72
x2 – 2x +1 + (y + 1)2 = 49
x2 – 2x + 1 + y2 + 2y + 1 – 49 = 0
x2 – 2x + y2 + 2y – 47 = 0
Hence the required equation of the given circle is x2 – 2x + y2 + 2y – 47 = 0.
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