Suppose a circle is centered at the vertex (0,0) and has a radius of length 4.

Question

For which points on the circle is the x-coordinate equal to 1? Your first answer should have a positive y-value.

For which points on the circle is the x-coordinate equal to 3? Your first answer should have a positive y-value.

What is the equation of the graph of the circle?

Answer 1

I will start with the last part:

equation of the circle is
x^2 + y^2 = 16

so if x = 1 ....
1 + y^2 = 16
y^2 = 15
y = √15 , actually ± √15 , but you wanted the positive

repeat my steps for x = 3