We were gievn a question in tutorial last week asking us to calculate the Taylor series of the function f(x,y) = e^(x^(2) + y^(2)) to second order in h and k about the point x=0, y=0 I've got the forumla here with all the h's and k's in it and have it written down, but it's actually how to work it out that's confusing me. f(a,b) + 1/1! (hd/dx + kd/dy)f(a'b) etc.... My confusion is do you multiply out the brackets so you'd have- f(a,b) + 1/1! (hdf(a,b)/dx + kdf(a,b)/dy) So you do the derivatives and then sub in the values of x and y Or, do you leave it as it is the first tiem I wrote it and end up with- 1+ (hd/dx + kd/dx) +0.5(hd/dx + kd/dy)^2 etc I know there are more terms but I've so much trouble typing out mathematical terms on this computer! I know this is v.obvious etc but I just want to get this clear in my head cos I have a test this Wednesday at uni and I want to go in with a fighting chance! Thanks!