Question

_ABC is a right triangle where m_B = 90Á. The coordinates of A and B are (5, 0) and (2, 5), respectively. If the x-coordinate of point C is 7, what is the y-coordinate of C?
5

7

8

10

Answer 1

Since the triangle is a right triangle at point B, then line AB is perpendicular to line BC.
For perpendicular lines, the product of their slopes is -1.
Slope of AB = (5 - 0)/(2 - 5) = 5/-3 = -5/3
Slope of BC = (y - 5)/(7 - 2) = (y - 5)/5

-5/3(y - 5)/5 = -1
-5(y - 5)/15 = -1
-5(y - 5) = -15
y - 5 = 3
y = 3 + 5 = 8

Therefore, the y-coordinate of point C is 8.