1. ## Slope-intercept

Problem states -
Find the slope-intercept form of the equation of the line perpendicular to 4x+5y= -11, and containing the point (-7,6):

I came up with y= - 4/5x + 2/5

Is this right? I feel like the example I am following from the book is not the way the instructor was telling the class. I am not sure if I am even understanding the book example. I'm not sure if I am doing the right steps at all.

2. ## Re: Slope-intercept

Originally Posted by Kibbygirl
Problem states -
Find the slope-intercept form of the equation of the line perpendicular to 4x+5y= -11, and containing the point (-7,6):

I came up with y= - 4/5x + 2/5

Is this right? I feel like the example I am following from the book is not the way the instructor was telling the class. I am not sure if I am even understanding the book example. I'm not sure if I am doing the right steps at all.
How did you get 2/5 for the y intercept?

3. ## Re: Slope-intercept

I'm unsure if I did it right..
I did:

y-6= -4/5(x-[-7])
y-6 = -4/5x - 28/5
y= -4/5x - (-2/5)
y= -4/5 + 2/5

4. ## Re: Slope-intercept

Originally Posted by Kibbygirl
I'm unsure if I did it right..
I did:

y-6= -4/5(x-[-7])
y-6 = -4/5x - 28/5
y= -4/5x - (-2/5)
y= -4/5 + 2/5
It's easier to just transpose the equation of the line you have been given.

\displaystyle \begin{align*} 4x + 5y &= -11 \\ 5y &= -4x - 11 \\ y &= \frac{-4}{5}x - \frac{11}{5} \end{align*}

What are the gradient and the y-intercept?

5. ## Re: Slope-intercept

- 4/5 and 11/5?

6. ## Re: Slope-intercept

The gradient of the line you have been given is -4/5 so the line perpendicular to this has gradient +5/4. So you want the line with gradient +5/4 through the point (-7,6)

7. ## Re: Slope-intercept

So would the final answer be y= 5/4x+2?

8. ## Re: Slope-intercept

Not +2. Line is y=5/4x+c. (-7,6) has to be on line. So we need 6=-35/4+c. So 59/4=c
Line is y=5/4x+59/4
Multiply both sides by 4
4y=5x+59 (any other arrangement of this is OK)