Which equation models a parabola with a vertex
located at (4,6) and a directrix at y = 8?
a. (x – 6)2 = -4)
b. (7-6)2 = (x – 4)
c. (y – 4)2 = -8(x – 6)
d. (x – 4)2 = -8(y - 6)

Given: abcd is a square. prove: ac ? bd. we are given that abcd is a square. if we consider triangle aeb and triangle aed, we see that side is congruent to side ad because sides of a square are congruent. we know that side ae is congruent to side ae by using the . finally, we know that side de is congruent to side because the diagonals of a square bisect each other. therefore, triangle aeb is congruent to triangle aed by congruency. we see that angle aed and angle aeb are a linear pair, and congruent by cpctc. thus, the measure of these angles will be 90°, and diagonal ac is perpendicular to diagonal bd by the .