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What does the standard equation of a circle tell us about the circle?
Complete the square for y to match the standard equation of a circle.
Complete the square for both variables to match the standard equation of a circle.
Is the given circle written in the standard equation of a circle?
Center: (3,7)
Radius: 5
Center: (0,-5)
Radius: 4
Center: (-9,4)
Radius: 5sqrt(2)
Center: (3,0)
Radius: 1
Let's start by recalling the standard equation of a circle.
(x- h)^2+(y- k)^2= r^2
LHS+(x-3)^2=RHS+(x-3)^2
Write as a power
We obtained the standard equation of the circle, so we can identify its center and radius. The center of the circle is ( 3, 7) and its radius is 5.
Examining the given circle, we can see that there are two terms containing y-variable.
LHS+5^2=RHS+5^2
Split into factors
a^2+2ab+b^2=(a+b)^2
Calculate power
Add terms
Write as a difference
a+b=a-(- b)
Write as a power
Now we can see that the center of the given circle is ( 0, -5) and its radius is 4.
Once again, we want to write the standard equation of the given circle.
Rewrite 47 as 81+16-50
Commutative Property of Addition
Write as a power
Split into factors
a^2+2ab+b^2=(a+b)^2
a^2-2ab+b^2=(a-b)^2
LHS+50=RHS+50
Write as a power
Split into factors
sqrt(a* b)=sqrt(a)*sqrt(b)
Calculate root
a+b=a-(- b)
From the standard equation of the given circle, we can see that its center is ( -9, 4) and its radius is 5sqrt(2).
Similarly as in Part A, the squares are already given. However, let's rearrange the sum on the left-hand side by using Commutative Property of Addition to obtain the standard equation of the circle.