Outside tangents

Calculate the length of the line segment S₁S₂ if the circles k₁ (S₁, 8cm) and k2 (S₂,4cm) touch the outside.

Correct answer:

x =  12

Step-by-step explanation:

$$\begin{gathered} r_1=8\text{ cm } \\ {r}_2=4\text{ cm } \\ x=r_1+r_2=8+4=12 \end{gathered}$$

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