parallel and perpendicular

Question

A line has a slope of negative 8
.
?(a) What is the slope of the line parallel to? it?
?(b) What is the slope of the line perpendicular to? it?

Answer 1

 

let's play with numbers:

 

y=-8x+5

y=-8x+10

 

Those lines don't share any points obviously (y is equal -8x+5 or -8x+10, it cannot happen at once). So they are parallel.

So we could conclude that -8 is always the slope of the parallel line.

 

For the perpendicular slope,  you may just remember the rule or google it. The slope of your line multiplied by the slope of the perpendicular line gives you -1 (negative reciprocal)

 

So, the slope of the perpendicular line is 1/8.

 

 

 

 

 

 

Answer 2

If one line is parallel to another line then both lines have the same slope. Likewise, perpendicular lines have a a slope that is the negative reciprocal of the other.

 

a. The slope of the parallel line is -8.

b. The slope of the perpendicular line is the reciprocal of -8 multiplied by -1. The reciprocal of -8 = -1/8. Now multiply the reciprocal by -1. -1 * -1/8 = 1/8. That's your slope.