I'm doing questions about stationary points involving functions with two variables, and the first step is finding the partial 1st and 2nd derivatives with respect to x and y. But I also need to find df dxdy where d is the partial derivative symbol... My mind is completely blank, someone help meee!

firstly differentiate the equation partially with respect to x alone, so treat y as a constant. Then takes this new result and differentiate partially with respect to y alone, treating x as a constant. It doesnt matter which order you do this in, both results will be the same.