why is it saying invalid notation?

Timelimit: 1 hour, 30 minutes. 38:06 remaining. Suppose a circle is centered at the vertex (0, 0) and has a radius of length 3. a. For which points on the circle is the x-coordinate equal to 1? Your first answer should have a positive y-value. O 2sqrt2 Preview 2v2. Invalid notation. O -2sqrt2 Preview -2v2. Invalid notation. b. For which points on the circle is the x-coordinate equal to 2? Your first answer should have a positive y-value. O sqrt5 Preview V5. Invalid notation. O -sqrt5 Preview - V5. Invalid notation. c. What is the equation of the graph of the circle? x 2+y 2=9 Preview