What is the relationship between two lines whose slopes are −7 and 1/7?

Question

a) The lines are parallel to each other
b) The lines are mirror images of each other, reflected over the x-axis
c) The lines always cross at the origin.
d) The lines are mirror images of each other, reflected over the y-axis.
e) The lines are perpendicular to each other.

Answer 1

I am going to graph
y = -7x and y = (1/7)x for you

www.wolframalpha.com/input/?i=plot+y+%3D+-7x+%2B1,+y+%3D+(1%2F7)x+%2B1+from+-10+to+10

let you decide how they are related.
Notice Wolfram used a different scale for the y-axis than the x-axis,
making y = (1/7)x look like it falls on the x-axis. It doesn't !

suggestion: plot a few points for each one, draw the straight line on a 1:1 scale grid.

Answer 2

the lines are perpendicular to each other