Actually i fink i've solved it YAY ...sori...how do i delete this thread?
Hey guys
A pt P(x,y) moves so that its distance from (3,4) is proportional to its distance from (-1,2). Find the equation of the locus of P if the origin is a pt on the locus.
I seriously have no clue how to do this q. - i tried using direct variation i.e.
...
then subbing k into
Naturally it didn't work =P
Help please?
Thanx a lot.
Is this how u do it? Mayb it's wrong because the textbook's answer is actually instead of
Let pt (3,4) be A and pt (-1,2) be B.
AP is proportional to BP.
So is proportional to .
Therefore, AP = k × BP
Substitute in (0,0)
9 + 16 = k (1+4)
25 = 5k
Therefore, k = 5
Substitute k = 5 into the original equation.
Hence,
At a glance I don't see anything wrong with your answer (but there are a couple of typos in the earlier parts of the solution, x's where there should be y's).
The books answer would be correct if the second point was (1, 2) rather than (-1, 2) , so maybe there's a typo somewhere.