If the chord of contact of tangents from a point on the circle $$x^2+y^2=r_1^2$$ to the circle $$x^2+y^2=r_2^2$$ touches the circle $$x^2+y^2=r_3^2$$, then $$r_1, r_2$$ and $$r_3$$ are in

Find the equation of the circle passing through $$(1,-2)$$ and touching the $$X$$-axis at $$(3,0)$$.

Let $$L_1$$ be a straight line passing through the origin and $$L_2$$ be the straight line $$x+y=1$$. If the intercepts made by the circle $$x^2+y^2-x+3 y=0$$ on $$L_1$$ and $$L_2$$ are equal, then which of the following equations represent $$L_1$$

The radius of the circle whose center lies at $$(1,2)$$ while cutting the circle $$x^2+y^2+4 x+16 y-30=0$$ orthogonally, is units.