C: x^2+ y^2+2x-4y-4=0 and has a tangent from point (1,1) of
length 10.
2. Consider a circle C:x^2+y^2-4x-8y+k=0. Find the value of k if
a)C touches the circle x^2+y^2-28x-18y+196=0 externally.
b)C touches the circle x^2+y^2-16x-24y+207=0 internally.
更新1:
Why there is square root of 10 in Q1??
