Question

find the slope of the line through the points (9,-4) and (9,5)
1 0 undefined 9

Answer 1

\[m = \frac{y_2 - y_1}{x_2 - x_1}\]

Answer 2

That's the slope formula by the way where m = slope
\[(9,4) = (x_1, y_1) \space\text {and} (9,5) = (x_2,y_2)\]

Answer 3

And it really doesn't matter if it is (9,4) or (9,-4)

Answer 4

oops

Answer 5

where's the edit button?

Answer 6

Great work hero.

Answer 7

i'm sorry, so what is it?

Answer 8

Use the slope formula Hero gave you and plug in
\[x_1=9,y_1=-4,x_2=9, y_2=5\]

Answer 9

In other words replace x1 with 9
replace y1 with -4
replace x2 with 9
replace y2 with 5
and then simplify

Answer 10

But what happens in the denominator ?

Answer 11

1?

Answer 12

hmmm so you have 9-9 in the denominator since both x's are 9

Answer 13

9-9=0 right?

Answer 14

But when we have division by zero we call that what?

Answer 15

ohhhh

Answer 16

slope m = (5 -4)/ ( 9 -9) = 1/0
-> slope is undefined ( vertical line x = c)