The equation of the straight line passing through the point (9, –9) and parallel to the y-axis is:

1. y – 9 = 0

2. y + 9 = 0

3. x + 9 = 0

4. x – 9 = 0

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

The slope of a line parallel to the line passing through the points A(3, –7) and B(5, –7) is:

1. 2

2. 1

3. –1

4. 0

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