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:
Answer:
b=30
Step-by-step explanation:
The angle here is a right angle which is an angle that equals 90 degrees. You subtract that measure of the angle by 60 and you end up with 30.
Answer:
1 Pen cost $2.25
Step-by-step explanation:
Assume:
Cost of Pen = a
Cost of pencil = b
Cost of notebook = c
a = 3b -------------------(1)
c = 4a -------------------(2)
2a + 6b + c = $18 -----(3)
From equation (1), b = a ÷ 3 ---------(4)
Substitute equations (2) and (4) in equation (3)
2a + 6 * (a ÷ 3) + 4a = $18
2a + 2a + 4a = $18
8a = $18
a = $2.25
Therefore, 1 Pen cost $2.25
Answer:
Ed used 39/60 of one hour to complete his tasks.
Step-by-step explanation:
Find the least common denominator (LCD), which would be 20
Then, find how to get from 5 to 20 and 4 to 20.
Use division.
20/5 = 4, 20/4 = 5
After this, multiply the numerator to the according number.
2*4 = 8 = 8/20
1*5 = 5 = 5/20
Make the denominator 60 to represent 60 minutes in one hour
5/20*3/3 = 15/60
8/20*3/3 = 24/60
Add the two results.
15/60 + 24/60 = 39/60