SAT Subject Test Mathematics Level 1

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