Question

Write an equation for the line that is perpendicular to the line x-3y=9 at the x-intercept.

Answer 1

What is the slope of a line perpendicular to the line x-3y=9 ?

Answer 2

3

Answer 3

right, and if you know the line goes through the x-intercept of x-3y=9, then you can find the y-coord of that intercept. Then you have a point and a slope of the perpendicular line, and you should be able to write the equation.

Answer 4

y=3x-3?

Answer 5

is that correct?

Answer 6

I'm working it, just a sec

Answer 7

ok

Answer 8

That's what I got, but I did it fast... might have made an error, so double check

Answer 9

how did u get y=-3x+27?

Answer 10

make original equation into y=mx+b
x-3y=9
3y=x-9
y=(1/3)x - 3
The slope is (1/3), and the y intercept is (0,-3).
I also found the x intercept at (9,0)

Then the perp. line has a slope that is the negative inverse, or - 1/(1/3) = -3
I then used the x intercept value as a point and the slope of -3 to get the equation of the perp line

Answer 11

The reason I used the x intercept for the point is that the problem said the perp line goes through that point

Answer 12

so the equation would be y=-3x-3?

Answer 13

The x intercept point from the original line is (9,0). That point isn't on the line equation you just wrote.

Answer 14

you got the slope right, but the intercept wrong.

Answer 15

I thought to myself, "hmmm... perp line must be y = -3x + b, and I knew that (9,0) was on the line, so I put in x=9 and y = 0 and found that b must be = 27."

Answer 16

ohh i see

Answer 17

I gotta run... sorry to leave abruptly, but hope this is helping...

Answer 18

thanks

Answer 19

glad to help :) good luck!