Answer:
see explanation
Step-by-step explanation:
Calculate the slope m using the slope formula
m = (y₂ - y₁ ) / (x₂ - x₁ )
with (x₁, y₁ ) = 2,4 ) and (x₂, y₂ ) = (5, 1)
m =  =
  =  = - 1 ← negative slope
 = - 1 ← negative slope
Repeat
with (x₁, y₁ ) = - 7,8) and (x₂, y₂ ) = (- 7, 0)
m =  =
 = 
Division by zero is undefined, thus slope is undefined.
Repeat with
(x₁, y₁ ) = (6, - 3) and (x₂, y₂ ) = (- 4, - 3)
m =  =
 =  = 0 ← zero slope
 = 0 ← zero slope
Repeat with
(x₁, y₁ ) = (3, 5) and (x₂, y₂ ) = (- 1, 2)
m =  =
 =  =
 =  ← positive slope
 ← positive slope