use x and y in a matrix

I want calculate D(x,y) after running code.

clear;
clc;
syms x y;
E=cell(3,1);
E{1}=[1,1,1;1,2,0;3,5,2];
E{2}=[1,0,0;3,2,1;0,4,3];
E{3}=[0,1,1;0,2,1;2,6,1];
A=[1;5;7];
B=[2,3,4];
C(x)=A+x*B;
D(x,y)=E{y}*C;
D(1,2)

But it returns error. Can someone help please?

Invalid indexing or function definition. Indexing must follow MATLAB indexing. Function arguments must be symbolic
variables, and function body must be sym expression.

Answer 1

[Steven Lord]

syms x y;
E=cell(3,1);
E{1}=[1,1,1;1,2,0;3,5,2];
E{2}=[1,0,0;3,2,1;0,4,3];
E{3}=[0,1,1;0,2,1;2,6,1];
A=[1;5;7];
B=[2,3,4];
C=A+x*B;
D = @(xin,y) subs(E{y}*C, x, xin);
D(1,2)

ans =