Line CD contains points A (4, −7) and B (4, 8). The slope of line CD is

+2

(1) Answers

Peick965

Given two points; A(x₁,y₁) and B(x₂,y₂) the slope "m" is:
m=(y₂-y₂)/(x₂-x₁) or m=(y₁-y₂)/(x₁-x₂)
In this case:
A(4,-7)
B(4,8)
m=(-7-8) / (4-4)=-15/0 because we have "0" in the denominator the line is vertical, and its slope is indefinitely.