GRE Subject Test: Math : Circles

Study concepts, example questions & explanations for GRE Subject Test: Math

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Example Questions

Example Question #1 : Circles

What is the equation of a circle with center at  and a radius of ?

Possible Answers:

Correct answer:

Explanation:

Step 1: Recall the general equation for a circle (if the vertex is not at :

, where center=

Step 2: Recall the shift of the graph..

If the value of  is positive, it will be shown as a negative shift in the equation.
If the value of  is negative, it will be shown as a positive shift in the equation.
If the value of  is positive, it will be shown as a negative shift in the equation.
If the value of  is negative, it will be shown as a positive shift in the equation.

Step 3: Look at the center given in the problem and find the rule(s) in step 2 that will apply:

Center=

Step 4: Plug in  into the equation of a circle:


Simplify:

Example Question #2 : Circles

What is the vertex of the equation of a circle: 

Possible Answers:

Correct answer:

Explanation:

Step 1: There are no numbers next to  and , so their is no movement of the vertex..

Step 2: Recall the vertex of a circle that does not move...

The vertex of this circle is .

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