Can someone help me on the following?
I need to find the slope and y-intercept:
x = -9
Thanks,
Ashley
When you have the equation of a line which contains only one
variable x or y, insert the term "+ 0x" if x is missing and
"+ 0y" if y is missing.
In the equation of the line
x = -9
the letter y is missing, so insert "+ 0y"
x + 0y = -9
Get some points by choosing arbitrary values for
the missing letter y:
x | y
| 3
| -2
| 4
| -5
Substitute y = 3 into
x + 0y = -9 x | y
x + 0(3) = -9 -9 | 3
x + 0 = -9 | -2
x = -9 | 4
| -5
Substitute y = -2 into
x + 0y = -9 x | y
x + 0(-2) = -9 -9 | 3
x + 0 = -9 -9 | -2
x = -9 | 4
| -5
Substitute y = 4 into
x + 0y = -9 x | y
x + 0(4) = -9 -9 | 3
x + 0 = -9 -9 | -2
x = -9 -9 | 4
| -5
Substitute y = -5 into
x + 0y = -9 x | y
x + 0(-5) = -9 -9 | 3
x + 0 = -9 -9 | -2
x = -9 -9 | 4
-9 | -5
So plot the points (-9,3), (-9,-2), (-9,4) and (-9,-5)
and draw a line through them
It is vertical. It will never cross the y-axis because
it is parallel to it, so there can be no y-intercept.
Now for the slope. You can just learn that the slope of
a vertical line is undefined. Or if you forget that,
you can try to find the slope by either of two ways:
1. Solving for y, getting equation in for y = mx + b.
But you cannot do that because there is no y to solve for.
2. Choosing two points on the line and using the slope
formula
y2 - y1
m = ---------
x2 - x1
Say we choose the two points (-9,4) and (-9,-5)
(x1,y1) = (-9,4) and (x2,y2) = (-9,-5)
have
(-5) - (4)
m = -------------
(-9) - (-9)
-9
m = --------
-9 + 9
-9
m = -----
0
But we cannot divide by zero,
so the slope is undefined.
So the answer is "There is no slope or y-intercept"
Edwin
