Question

Which lines are perpendicular to the line y – 1 = (x+2)? Check all that apply.

y + 2 = –3(x – 4)
y − 5 = 3(x + 11)
y = -3x –
y = x – 2
3x + y = 7

Answer 1

None!

Explanation:

Two lines are perpendicular when the product of their slopes equals -1.

The general equation of a line is:

y = m(x-x0) + y0. Where "m" represents the slope and (x0, y0) a point on the line.

Then, we find the slope of each equation:

a) y + 2 = –3(x – 4) -> m=-3

b) y − 5 = 3(x + 11) -> m=3

c) y = -3x -> m= -3

d) y = x – 2 -> m=1

e) 3x + y = 7 -> m= -3

And the slope of the line y – 1 = (x+2) is m=1.

So, multiplying the slopes:

a) -3 * 1 = -3

b) 3 * 1 = 3

c) -3 * 1 = -3

d) 1 * 1 = 1

e) -3 * 1 = -3

None of the lines are perpendicular to the line y – 1 = (x+2)