求高人指点：符号计算，提示错误
 

??? Undefined function or method 'mtimes' for input arguments of type 'cell'.

Error in ==> WALL at 3
A=simplify(2*[(B/2).^3+(3*B/2+H).^3-(B/2+H).^3+(3*B/2+2*H+Q).^3-(3*B/2+H-Q).^3+(3*B/2-Q).^3-(B/2+2*H+Q).^3+(B/2+Q+H).^3-(B/2-Q).^3+(B/2-H-Q).^3]+6*{(C+2*H).*[(B/2+H/2).^2+(3*B/2+3*H/2).^2+(3*B/2+H/2-Q).^2+(B/2+3*H/2+Q).^2+(B/2-Q-H/2).^2]}+3*[(3*B/2+5*H/2+Q).^2.*(C+3*H+Q)+(3*B/2+5*H/2+Q).^2.*(Q+2*H)])
程序：

syms H C Q
B=3*Q+2*H;
A=simplify(2*[(B/2).^3+(3*B/2+H).^3-(B/2+H).^3+(3*B/2+2*H+Q).^3-(3*B/2+H-Q).^3+(3*B/2-Q).^3-(B/2+2*H+Q).^3+(B/2+Q+H).^3-(B/2-Q).^3+(B/2-H-Q).^3]+6*{(C+2*H).*[(B/2+H/2).^2+(3*B/2+3*H/2).^2+(3*B/2+H/2-Q).^2+(B/2+3*H/2+Q).^2+(B/2-Q-H/2).^2]}+3*[(3*B/2+5*H/2+Q).^2.*(C+3*H+Q)+(3*B/2+5*H/2+Q).^2.*(Q+2*H)])