Equation of circle whose center is (h,k) i.e "‌(x−h)2+(y−k)2=k2
(radius of circle =k because circle is tangent to x-axis) Equation of circle passing through (−1,+1) ‌∴(−1,−h)2+(1−k)2=k2 ‌⇒1+h2+2h+1+k2−2k=k2 ‌⇒h2+2h−2k+2=0 ‌D≥0 ∴(2)2−4×1.(−2k+2)≥0 ⇒4−4(−2k+2)≥0 ⇒1+2k−2≥0 ⇒k≥‌