Let the equation of the circle is x2+y2+2gx+2fy+c=0 This circle touch the coordinate axes and lying in the first quadrant, then g2−c‌=0‌ and ‌f2−c=0 g‌=±√c,f=±√c circle lies in first quadrant ∴ The centre is (√c,√c) If the line 4x+3y−12=0 touch the circle, then ‌√f2+g2−c=‌