I'm begginer in maple so I have many questions

I have 

f1 := [x2^3-3*x1+x2, -x2-x3+u, x2-2*x3]

I want to put 

x1=2*x1

x2=2*x2

x3=5*x3

and I wand it in loop

for x4,...xn

so that f1 will be a vector

I have s := [[x[1] = 0, x[2] = 0, x[3] = 0]]

when I use s in

J1 := eval(Ja, s)

This message appear 

Error, invalid input: eval expects its 2nd argument, eqns, to be of type {integer, equation, set(equation)}, but received s

 But When I wrote 

J1 := eval(Ja, [x[1] = 0, x[2] = 0, x[3] = 0]), it runs well

I need the solution for first one since s created automaticly 

what should I do?