x^2-ky+3=0 represents a parabola whose focus is in (0,2) find k
What have you tried? Princeps post tell's what you have to do, namely:
The equation of the parabola is:
$\displaystyle y=\frac{x^2+3}{k}$
Therefore we can find $\displaystyle k$ by solving the equation:
$\displaystyle \frac{-D}{4a}=2 \Rightarrow \frac{4ac-b^2}{4a}=2$
Proceed.