Two non-vertical lines with slopes m₁ and m₂ are parallel to each other, if:

1. m₁m₂ = 1

2. m₁m₂ = –1

3. m₁ = –m₂

4. m₁ = m₂

Two non-vertical lines with slopes m₁ and m₂ are perpendicular to each other, if:

1. m₁.m₂ = 1

2. m₁.m₂ = –1

3. m₁ = –m₂

4. m₁ = m₂

The slope of a line perpendicular to the line passing through the points P(3, –4) and Q(1, –8) is:

1. $\dfrac{-1}{2}$

2. 2

3. $\dfrac{1}{2}$

4. –2

The slope of a line parallel to the line, 3x – 5y + 8 = 0, is:

1. $\dfrac{-5}{3}$

2. $\dfrac{5}{3}$

3. $–\dfrac{3}{5}$

4. $\dfrac{3}{5}$