Write an equation for a line perpendicular

[Gadsilla]

I don't understand it. I have the answer, but I don't get it. Could someone please explain ?

Write an equation for a line perpendicular to y=−4x−4 and passing through the point (4,3)
y=

 

[Deleted member 4993]

I don't understand it. I have the answer, but I don't get it. Could someone please explain ?

Write an equation for a line perpendicular to y=−4x−4y=-4x-4 and passing through the point (4,3)
y=

Suppose the line you want to draw is J₁. You are given the equation of a line (J₂) - perpendicular to J₁.

Can you calculate the slope of the line J₁ from the given data?

 

[Dr.Peterson]

I don't understand it. I have the answer, but I don't get it. Could someone please explain ?

Write an equation for a line perpendicular to y=−4x−4 and passing through the point (4,3)
y=

It looks like you copied the problem from some homework software. Often there will be a source of examples to teach you how to solve the problem. Is that available? Have you looked at it in order to learn this topic?

It will probably have told you that if two lines are perpendicular, then the slope of one is the "negative reciprocal" of the other -- that is, once you find the slope of the given line, you can flip that over and change the sign to get the slope you need for your line.

Then, you should have learned one of two main ways to write the equation of a line given a point and a slope: the point-slope form, and solving for b. What method have you been taught?

 

[Gadsilla]

I put in the wrong question, complete dunce mode.
Write an equation for a line perpendicular to y = -4x -4 and passing through the point (4,3)
y=

So this is what I did

y=mx+b

3=4x+b

Then I get stuck :/

 

[sinx]

I put in the wrong question, complete dunce mode.
Write an equation for a line perpendicular to y = -4x -4 and passing through the point (4,3)
y=

So this is what I did

y=mx+b

3=4x+b

Then I get stuck :/

what is the slope of a line perpendicular to y=-4x -4?
[slope= 1/4, draw a graph of y=-4x -4 and you will see the perpindicular slope is not 4]

y=mx+b, with (4,3) and m=1/4, find b.

 

[Gadsilla]

what is the slope of a line perpendicular to y=-4x -4?
[slope= 1/4, draw a graph of y=-4x -4 and you will see the perpindicular slope is not 4]

y=mx+b, with (4,3) and m=1/4, find b.

I don't get m = 1/4. How ?

 

[pka]

I put in the wrong question, complete dunce mode.
Write an equation for a line perpendicular to y = -4x -4 and passing through the point (4,3)

The general equation of a line is $\displaystyle Ax+By+C=0$.
If $\displaystyle A\cdot B\ne 0$ then the line is neither vertical nor horizontal. So the slope is $\displaystyle \dfrac{-A}{B}$ & the y-intercept is $\displaystyle \dfrac{-C}{B}$.
Now the line $\displaystyle Bx-Ay+C=0$ is perpendicular to the given line. If we want that perpendicular to pass through $\displaystyle (p,q)$ then $\displaystyle C=Aq-Bp$.

 

[Gadsilla]

The general equation of a line is $\displaystyle Ax+By+C=0$.
If $\displaystyle A\cdot B\ne 0$ then the line is neither vertical nor horizontal. So the slope is $\displaystyle \dfrac{-A}{B}$ & the y-intercept is $\displaystyle \dfrac{-C}{B}$.
Now the line $\displaystyle Bx-Ay+C=0$ is perpendicular to the given line. If we want that perpendicular to pass through $\displaystyle (p,q)$ then $\displaystyle C=Aq-Bp$.

Where does the A & B come from ?

 

[Gadsilla]

what is the slope of a line perpendicular to y=-4x -4?
[slope= 1/4, draw a graph of y=-4x -4 and you will see the perpindicular slope is not 4]

y=mx+b, with (4,3) and m=1/4, find b.

I don't get 1/4 when I draw the graph. How did you get it ?

 

[pka]

Where does the A & B come from ?

@Gadsilla, are you really doing a course in algebra?
If you are then you should know that rules are given the abstract,
If you do not understand that simple fact, no wonder you have are having trouble.

what is the slope of a line perpendicular to y=-4x -4?
[slope= 1/4, draw a graph of y=-4x -4 and you will see the perpindicular slope is not 4]
y=mx+b, with (4,3) and m=1/4, find b.

In the above we have line $\displaystyle 4x+y+4=0$.
Thus $\displaystyle A=4,~B=1,~\&~C=4$.

 

[Gadsilla]

@Gadsilla, are you really doing a course in algebra?
If you are then you should know that rules are given the abstract,
If you do not understand that simple fact, no wonder you have are having trouble.


In the above we have line $\displaystyle 4x+y+4=0$.
Thus $\displaystyle A=4,~B=1,~\&~C=4$.

\(\displaystyle

I'm doing calculus 1. However, when I'm facing issues I'm often told that I should know it by now so I never really manage to learn it.\)

 

[sinx]

I don't get 1/4 when I draw the graph. How did you get it ?

1/4 is the negative reciprocal of -4.
(perpendicular slopes are negative reciprocals.)

on your graph you should see that 1/4 and -4 slopes are perpendicular.
[and 3 is perpendicular to -1/3 and so on]
but prove it to yourself. Then you won't forget it.
[free advice]

 

[Gadsilla]

1/4 is the negative reciprocal of -4.
(perpendicular slopes are negative reciprocals.)

on your graph you should see that 1/4 and -4 slopes are perpendicular.
[and 3 is perpendicular to -1/3 and so on]
but prove it to yourself. Then you won't forget it.
[free advice]

It makes sense How would I find b ?

 

[sinx]

It makes sense How would I find b ?

y=mx+b, with (4,3) and m=1/4, find b.

 

[Gadsilla]

y=mx+b, with (4,3) and m=1/4, find b.

I don't get it since b isn't 2.75.

 

[sinx]

I don't get it since b isn't 2.75.

y=mx+b
(4,3); m=1/4
3=(1/4)4+b

 

[Gadsilla]

y=mx+b
(4,3); m=1/4
3=(1/4)4+b

Yeah it finally made sense, thank you.

 

[Deleted member 4993]

Yeah it finally made sense, thank you.

So what did you get for 'b'?

 

[Gadsilla]

So what did you get for 'b'?

I got 2 for b.

y=1/4x+2

 

[mmm4444bot]

I got 2 for b.

y=1/4x+2

Looks good.