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Question -

Find the equation of the circle which touches the axes and whose centre lies on x – 2y = 3.



Answer -

Let us assume thecircle touches the axes at (a, 0) and (0, a) and we get the radius to be |a|.

We get the centre ofthe circle as (a, a). This point lies on the line x – 2y = 3

a – 2(a) = 3

-a = 3

a = – 3

Centre = (a, a) = (-3,-3) and radius of the circle(r) = |-3| = 3

We have circle withcentre (-3, -3) and having radius 3.

We know that theequation of the circle with centre (p, q) and having radius ‘r’ is given by: (x– p)2 + (y – q)2 = r2

Now by substitutingthe values in the equation, we get

(x – (-3))2 +(y – (-3))2 = 32

(x + 3)2 +(y + 3)2 = 9

x2 +6x + 9 + y2 + 6y + 9 = 9

x2 + y2 +6x + 6y + 9 = 0

The equation of thecircle is x2 + y2 + 6x + 6y + 9 = 0.

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