Below is a question from a recent SAT exam. It is a non-calculator question that would typically take a student 1-2 minutes to complete.
A circle in the xy-plane has center (5, 7) and radius 2. Which of the following is an equation of the circle?
(A)
(B)
(C)
(D)
To begin, we will recall the formula for the equation of a circle
Where a is the x-coordinate for the centre of the circle, b is the y-coordinate of the centre of the circle, and r is the radius.
We are told in the question that the circle has a radius of 2. Therefore,
Our equation now looks like this.
Next, we substitute a and b for the values given as the circle's centre.
and
So, the answer is A.
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