A circle

A circle relation is given to be x² + y² =16. What is the radius of the circle?

Correct answer:

r =  4

Step-by-step explanation:

$$\begin{gathered} x^2+y^2=16 \\ (x-x_0{)}^2+(y-yo{)}^2=r^2 \\ {x}_0=y_0=0 \\ {r}^2=16 \\ r=\sqrt{16}=4 \end{gathered}$$

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