Cho hàm số f(x, y)= a/ tính vi phân cấp 1 của hàm số tại (1,1)
b/ tính các đạo hàm riêng cấp 2 của hàm số tại (1,1)
c/ chứng minh rằng không tồn tại lim(x, y)->(0,0) f(x, y)
giúp mình nha

Linda and ralph have signed a contract to purchase a home. the closing date is april 27, and the buyer owns the property on the day of closing. the selling price of the home is $782,500. linda and ralph obtained a fixed-rate mortgage from a bank for $685,000 at 7.35% interest. the seller has already paid $14,578.15 in property taxes for the coming year. how much will linda and ralph owe in prorated expenses? (3 points) $64,925.65 $34,347.06 $10,496.82 $9,945.06