Answer:
(-8, 7); x + y = 13 → y= -x + 13
parallel lines have the same slope. slope is -1
y = -x + b
7 = -(-8) + b
7 = 8 + b
b = -1
(a) y = -x - 1
perpendicular lines have opposite slopes. slope is 1/2.
y = -1/2x + b
7 = -1/2(-8) + b
7 = 4 + b
b = 3
(b) y = -1/2x + 3
