another QR

[yorkiepoo]

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How do you determine the the new y intercept when you are finding the perpendicular line like in the following example:

which of the following is the equation of the line that contains the point (3, -1) and is perpendicular to the line y = 3x +3 ?

 

[wigglytooth]

How do you determine the the new y intercept when you are finding the perpendicular line like in the following example:

which of the following is the equation of the line that contains the point (3, -1) and is perpendicular to the line y = 3x +3 ?

The slope of the line perpendicular to the line given is the negative reciprocal of the given slope. Therefore the new m= -1/3.

So from there u plug and chug with the point you're given--> y = -1/3 X + b --> -1 = (-1/3)(3) + b

 

[yorkiepoo]

The slope of the line perpendicular to the line given is the negative reciprocal of the given slope. Therefore the new m= -1/3.

So from there u plug and chug with the point you're given--> y = -1/3 X + b --> -1 = (-1/3)(3) + b

right.. i got that far.. but it still leaves a few options with b = 0, +2 or -2....

???

 

[wigglytooth]

right.. i got that far.. but it still leaves a few options with b = 0, +2 or -2....

???

-1 = (-1/3)(3) + b --> -1 = -1 +b --> b = 0

Where are u getting the +/- 2?

 

[tinman831]

right.. i got that far.. but it still leaves a few options with b = 0, +2 or -2....

???

To find B, the Y-intercept, just plug in the coordinates for the point (3,-1) orginally given in the problem and solve to find B. Then you get the answer wigglytooth showed in the previous post.