locus problem (1 Viewer)

[wolf7]

Find the equation of the locus of point p(x,y) that , moves so that it is always 9 units from the point (-1,-1)

plz show working out

 

[wolf7]

sry, already got the answer

 

[sf_diegoxrock]

is the answer.. x^2 + 2x + y^2 + 2y = 0 ??

 

[Riviet]

No, you need to factorise it by completing the square.

 

[sf_diegoxrock]

oh really? im using 'maths in focus' at the moment and they don't factorise it but yeah no worries, thanks for that


while you're here hehe

Here's a slight variation on the second using product of roots:
let the roots be k and k+1, then:
k(k+1)=2
k^2+k=2
k^2+k-2=0
(k+2)(k-1)=0
.: k= -2, 1

Now if we use sum of roots then we get this:
k+k+1= -m
sub. values of k in
-4+1=-m
m= 3
1+1+1=-m
m=-3

you said that in a recent post.. just wondering.. why did you times to two roots to equal 2??? where does 2 come from???

 

[Riviet]

I can't find the thread with the post that i made but product of roots equals c/a