When you’re trying to find an equation that fits a graph, pick a point or
two from the graph and try them in the equations.
CIRCLES AND PARABOLAS
The only curved graphs you’ll find on a Math 1 test are circles and parabolas.
Like slope-intercept questions, these questions are essentially algebraic.
Circles questions, like Example 5, are often just a matter of recalling and
applying the appropriate equation.
CIRCLE
The equation of a circle centered at (h, k) and with radius r is (x − h)^2 +
( y − k)^2 = r^2.
Example 5
Which of the following equations describes the set of all points (x, y) in
the coordinate plane that are a distance of 5 from the point (–3, 4)?
1.
(A) (x + 3) + (y − 4) = 5
(B) (x − 3) + (y + 4) = 5
(C) (x + 3)^2 + (y − 4)^2 = 5
(D) (x + 3)^2 + (y − 4)^2 = 25
(E) (x − 3)^2 + (y + 4)^2 = 25