Linear relationships can be expressed in a graphical format where the variable and the constant are connected via a straight line or in a mathematical format where the independent variable is multiplied by the slope coefficient, added by a constant, which determines the dependent variable.
We know that:

is an equation of a circle.
When we substitute x and y (from the pairs we have), we'll get a system of equations:

and all we have to do is solve it for a, b and r.
There will be:

From equations (II) and (III) we have:

and from (I) and (II):

Now we can easly calculate a and b:

Finally we calculate

:

And the equation of the circle is:
i'm not sure how to solve the first one but the second is 150
Answer: 4
Step-by-step explanation:
The worth of Sarah's investment when she is 68 is $14,728.51.
<h3>What is the worth of the investment?</h3>
The formula that can be used to determine the worth of the investment is:
FV = P (1 + r)^n
FV = Future value
P = Present value
R = interest rate
N = number of years = 68 - 18 = 50
$500 x (1.07)^50 = $14,728.51
To learn more about future value, please check: brainly.com/question/18760477