Given two circles $x^2+y^2+8 x-6 y-24=0$ and $x^2+y^2-4 x+10 y+20=0$. Then they are

Given two circles $x^2+y^2+8 x-6 y-24=0$ and $x^2+y^2-4 x+10 y+20=0$. Then they are
  1. Disjoint.
  2. Concentric,
  3. Touching internally
  4. Touching externally.

Solution

$\begin{aligned} & x^2+y^2+8 x-6 y-24=0, C_1 \equiv(-4,3), r_1=7 \\ & x^2+y^2-4 x+10 y+20=0, C_2 \equiv(2,-5), r_2=3 \\ & C_1 C_2=\sqrt{(2+4)^2+(-5-3)^2}=10 \text { and } r_1+r_2=7+3=10 \end{aligned}$ $\because C_1 C_2=r_1+r_2$ hence, the two circles touching externally

Asked in: MHT CET 2022 (11 Aug Shift 1)

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