Understanding Circle Functions - High School Math
Card 0 of 2
Find the radius of the circle given by the equation:
Find the radius of the circle given by the equation:
To find the center or the radius of a circle, first put the equation in the standard form for a circle: 
, where 
is the radius and 
is the center.
From our equation, we see that it has not yet been factored, so we must do that now. We can use the formula 
.
, so 
.
and 
, so 
and 
.
Therefore, 
.
Because the constant, in this case 4, was not in the original equation, we need to add it to both sides:
Now we do the same for 
:
We can now find 
:
To find the center or the radius of a circle, first put the equation in the standard form for a circle:
From our equation, we see that it has not yet been factored, so we must do that now. We can use the formula
Therefore,
Because the constant, in this case 4, was not in the original equation, we need to add it to both sides:
Now we do the same for
We can now find
Compare your answer with the correct one above
Find the center of the circle given by the equation:
Find the center of the circle given by the equation:
To find the center or the radius of a circle, first put the equation in standard form: 
, where 
is the radius and 
is the center.
From our equation, we see that it has not yet been factored, so we must do that now. We can use the formula 
.
, so 
.
and 
, so 
and 
.
This gives 
.
Because the constant, in this case 9, was not in the original equation, we must add it to both sides:
Now we do the same for 
:
We can now find the center: (3, -9)
To find the center or the radius of a circle, first put the equation in standard form:
From our equation, we see that it has not yet been factored, so we must do that now. We can use the formula
This gives
Because the constant, in this case 9, was not in the original equation, we must add it to both sides:
Now we do the same for
We can now find the center: (3, -9)
Compare your answer with the correct one above