Question

Are the lines perpendicular?

no, because the slopes of the lines are equal
no, because the slopes of the lines are not opposite reciprocals
yes, because the slopes of the lines are equal
yes, because the slopes of the lines are opposite reciprocals

Answer 1

To tell if two lines are perpendicular, you just have to look at the slopes. Perpendicular lines have opposite reciprocal slopes. Basically if we had a linear equation like:

y = 4x - 12

then the perpendicular version would be:

y = -1/4x + 13

Basically just change the sign and flip the slope. (the y-intercept is of course going to change as well, since they aren’t going to be on the same line).