Remember that .
Now using this we can square things and add them
However, this doesn't get rid of the or the . We need both of these terms to have the same number in front of them, but they don't right now. So we could have squared the x term then multiplied the y term by squared it and then added them. The following is the result
. Finally, the solution to a) is
For the last two, I am unsure how you find the gradient of a function at your level. What has your instructor defined as the gradient and is there a formula?