9.當存在其值為一3。請問下列哪個選項是正確的? (A)a=0(B)a?=9(C)a=-3(D)a=3(E)以上皆非。

複選題11.當f(x,y)=x2+y2+y2texp(2-y),且F(T,3,z)=f(xy)一z。請問下列哪些選項是正確的? (A) (B)(C)∇F at the point (1,2,-1) is (1,3, -1)T. (D) The tangent plane to the graph of the function F(x, y) at the point (1, 1,3) is 3(c-1)+ (V-1)- (z-3)=0. (E) The minimum value of f(c, y) is 0.