A circle touches the X-axis and the line 4x-3y+4=0 both. If the centre lies on the line x-y-q=0 in the third quadrant, then the equation of the circle is
A
9(x2+y2)+24x+3y-16=0
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B
3(x2+y2)+8x+2y+1=0
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C
9(x2+y2)+6x+24y+1=0
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D
3(x2+y2)+2x+8y+1=0
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Solution
The correct option is A 9(x2+y2)+24x+3y-16=0 Circle touches x-axis, y=0 and line 4x−3y+4=0 Equation of circle can be written as x2+y2+2gx+2fy+c=0 Tangent to the circle (x1,y1) can be written as xx1+yy1+g(x+x1)+f(y+y1)+c=0y=0x−3y+4=0y=x−9x=0,y=−9x=9y=0(9,0)9x+g(x+a)+fy+c=09x+gx+gq+fy+c=0x(9+g)+fy+c+gq=09+g=4f=−3x−y−9=0−g+f−9=0−g−q=−f−g−q=3 Solving them, we will get g=−12 Equation of circle 9(x2+y2)+24x+3y−16=0