solving system of non linear equations

sym x;
sym a1;
sym a2;
sym a3;
sym a4;
sym u1;
sym u2;
sym u3;
sym u4;
u=a1+a2*x+a3*(x^2)+a4*(x^3);
l=1;
eqn=[subs(u,x,0)-u1==0,subs(diff(u(x),x),x,0)-u2==0,subs(u,x,l)-u3==0,subs(diff(u(x),x),x,l)-u4==0];
[a1, a2, a3, a4]=solve(eqn);

It is showing error.Is there anything wrong with the code?

Answer 1

[Walter Roberson]

Those "sym" need to be "syms"

syms x a1 a2 a3 a4 u1 u2 u3 u4

also, you need to define u as

u(x) = a1+a2*x+a3*(x^2)+a4*(x^3);

[naveen badri]

I is executed,but the equation is not solved.

After executing when i am giving a1 as input in command window, it is giving just a1 but not the value of a1 after solving. This is the code.

syms x a1 a2 a3 a4 u1 u2 u3 u4;
u(x)=a1+a2*x+a3*(x^2)+a4*(x^3);
l=1;
eqn=[subs(u,x,0)-u1==0,subs(diff(u(x),x),x,0)-u2==0,subs(u,x,l)-u3==0,subs(diff(u(x),x),x,l)-u4==0];
[a1, a2, a3, a4]=solve(eqn);

[Walter Roberson]

[a1, a2, a3, a4]=solve(eqn, a1, a2, a3, a4);

It was solving for the u variables by default.

[naveen badri]

thank you sir