Hi All

I'm studing for as level exam. I'm stuck on a simultaneous equiation
question. I would be greatful for any advice. The question follows. It
is right out of the cambridge press text book question 8 revision
exercise 1 module 1 (2002 press):-


Find the values of k such that the straight line y=2x+k meets the curve
with equation
 x^2 + 2xy +2y^2 =5 exactly once.

The answer from the back is +- square root of 65

Your help would be much appreciated.

Thanks

Paul