Just another parametrics q. (1 Viewer)

[Aysce]

Hey BOSers, question is:

The chord of contact of two tangents drawn from an external point P to the parabola x^2=8y has equation x+2y-3=0. Find the coordinates of P. Thanks in advance guys

 

[asianese]

Hey BOSers, question is:

The chord of contact of two tangents drawn from an external point P to the parabola x^2=8y has equation x+2y-3=0. Find the coordinates of P. Thanks in advance guys

Equation of P : xx0 (subscript) = 2a(y+y0)

therefore x+2y-3 = xx0 -2a(y+y0)

x+2y-3= xx0 -2ay-2ay0

Now from the equation of the parabola, 8 = 4a, a=2

therefore
x+2y-3 = xx0 -4y-4y0

And I've probably done something wrong...

 

[Expense]

thats piss easy, come on

 

[Aysce]

Nope just checked the book and the answer is P(-2,-1.5) :/ show all working please

 

[Expense]

Come on idiots! How hard is it! Fuck

 

[taeyang]

Sorry, didn't have a calculator the first time.

if the image is too small, use this http://oi53.tinypic.com/2h6au55.jpg

 

[Aysce]

Thank you ^^