I defined two matrices; vectorC:=Matrix(1,4,symbol=c); vectorE:=Matrix([[e[0]],[e[1]],[e[2]],[e[3]]]); so I wrote the equation: eq3:=evalm(vectorC&*vectorE)=0; I solved e[1] as follows: solve(eq3,e[1]); However, it shows: Error, (in solve) invalid arguments, How can I solve the problems? Thanks