Question

Write an equation of a line with an undefined slope and passing through the point (-2,4).

Answer 1

If a line has undefined slope, then it is a very specific type of line. What kind of line is it that has undefined slope?

Answer 2

horizontal

Answer 3

No, horizontal lines have slope = 0, not undefined slope.

Right idea, wrong "special" line. :)

Answer 4

remember, undefined slope means that the den'r of the slope equation is =0.

Answer 5

okay so how would i find the slope there isnt one right?

Answer 6

You don't need the slope. You know that the slope is undefined.

I'm not asking you to find the slope; I'm asking, what kind of line is it, IF the slope is undefined?

Answer 7

The fact that the slope is undefined tells you WHAT KIND of line it is.

Just like, if the slope was 0, that would tell you that it was a horizontal line.

If the slope is undefined, then it is a ________ line.

Answer 8

it would be a straight line

Answer 9

All linear equations are "straight" lines.

There are two "special" kinds of lines. You can tell them by their slope.

If the slope=0, every y-coordinate on the line is the same, and hence you have a horizontal line.

If the slope is undefined, then every x-coordinate on the line is the same, and hence you have a VERTICAL line.

Answer 10

oh alright then how would i get the equation

Answer 11

Vertical lines don't depend on y at all, since every x-coordinate is the SAME on the line.

So the equation of the line is just x=a for some constant, a. Whatever that "same" x coordinate is.

So your line goes through the point (-2,4), so WHAT is the equation for the VERTICAL line through that point?

Answer 12

(My vertical line above, as an example, goes through the point (-5, 2) - so every x-coordinate is x=-5)

Answer 13

x=-5

Answer 14

No, that's the equation for MY line, in my example. Mine is just an example.

YOUR line goes through the point (-2,4). (My vertical line above does not go through that point.)

Answer 15

so x=-2??

Answer 16

Yes, exactly! :)

Answer 17

Because if it goes through (-2,4) and is vertical, then EVERY x-coordinate on the line is x=-2. That's the thing about vertical lines - they have the same x-coordinate, everywhere.

And horizontal lines have the same y-coordinate, everywhere.

Answer 18

alright thank you but my equation is y=-2

Answer 19

what equation is y= -2?

That is NOT an equation for a line with undefined slope. You said above, x= - 2....?