Answer:
x² + y² = 1
Step-by-step explanation:
A circle is the locus of a point such that its distance from a fixed point (known as the origin) is always constant. The general equation of a circle is given as:

Where (h, k) is the center of the circle and r is the radius of the circle.
Given that the plane is 1 unit from the point (0,0). Therefore the radius of the circle is 1 unit and the center of the circle is (0, 0). Therefore the equation of the circle is:

Use the compound interest formula.
A = P*(1 +r/n)^(n*t)
where P is the principal, r is the annual rate, n is the number of compoundings per year, and t is the number of years.
For the first investment, ...
A = 208,000*(1 +.08/4)^(4*5) = 309,077.06
For the second investment, ...
A = 218,000*(1 +.07/2)^(2*4) = 287,064.37
Totaling both investments at maturity, Megan has $596,141.43.