A locus question (1 Viewer)

[Thalandir]

Hey guys, I'm new to this site and I'm really sorry if this is the wrong place for this question.

I'm in Yr11 and right now we're studying Locus and the Parabola, and I've been finding it rather easy (I'm coming first in our class by miles) but I've reached this question and I'm not quite sure what to do. I take it that the solution is simple and that I'm going to hit myself over the head when someone points it out to me .

Question is: Find the equation of the locus of a point that moves so that its distance from the line 3x + 4y + 5 = 0 is always 4 units.

I know straight away that the locus is going to be a pair of parallel lines running along either side of 3x + 4y + 5 = 0, and that both will be 4 units away from that line, and that both will have the same gradient as 3x + 4y + 5 = 0, but I'm lost as to where to go from here. I checked the answer in the back to see if I could reverse-engineer it, but I'm honestly lost, anyone and all help would be greatly appreciated .

Thanks in advance, and I'm sorry if this thread is in the wrong place.

~Thal

 

[Timothy.Siu]

probably something to do with perp. distance is 4.

 

[shady145]

O:

 

[untouchablecuz]

enjoy

 

[shady145]

^mmmhmm

 

[Thalandir]

enjoy

Thankyou

Twas very helpful

 

[Drongoski]

enjoy

well done; that's the way to do it.

by the way: how do you get such professional mathematical typeset ?

 

[untouchablecuz]

thanks

i use microsoft office 07, it has an equation editor that has everything

then i screen shot it, and paste it on paint

LaTeX is way too fiddly for me

 

[Aquawhite]

LaTeX gets annoying because I just can't figure out how to use it very fast...

Easy and good solve though I must say I really dislike locus problems though.

 

[2gapple]

回复: A locus question

Hey guys, I'm new to this site and I'm really sorry if this is the wrong place for this question.

I'm in Yr11 and right now we're studying Locus and the Parabola, and I've been finding it rather easy (I'm coming first in our class by miles) but I've reached this question and I'm not quite sure what to do. I take it that the solution is simple and that I'm going to hit myself over the head when someone points it out to me .

Question is: Find the equation of the locus of a point that moves so that its distance from the line 3x + 4y + 5 = 0 is always 4 units.

I know straight away that the locus is going to be a pair of parallel lines running along either side of 3x + 4y + 5 = 0, and that both will be 4 units away from that line, and that both will have the same gradient as 3x + 4y + 5 = 0, but I'm lost as to where to go from here. I checked the answer in the back to see if I could reverse-engineer it, but I'm honestly lost, anyone and all help would be greatly appreciated .

Thanks in advance, and I'm sorry if this thread is in the wrong place.

~Thal

do you know this formula :d={Ax+By+C}/root(A^2+b^2) note :{} indicated absolutely value so you can get it easy
substitute it into the formula i.e: 3x+4y+25=0 and 3x+4y-15=0