Q19 of 184 Page 10

The centre of the circle is (2x - 1, 3x + 1) and radius is 10 units. Find the value of x if the circle passes through the point (- 3, - 1).

Given that the circle has centre O(2x - 1, 3x + 1) and passes through the point A(- 3, - 1) and has a radius(r) of 10 units.



We know that the radius of the circle is the distance between the centre and any point on the circle.


So, we have r = OA


OA = 10


OA2 = 100


(2x - 1 - (- 3))2 + (3x + 1 - (- 1))2 = 100


(2x + 2)2 + (3x + 2)2 = 100


4x2 + 8x + 4 + 9x2 + 12x + 4 = 100


13x2 + 20x - 92 = 0


13x2 - 26x + 46x - 92 = 0


13x(x - 2) + 46(x - 2) = 0


(13x + 46)(x - 2) = 0


13x + 46 = 0 (or) x - 2 = 0


13x = - 46 (or) x = 2



The values of the x are or 2.


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