defining an Unknown matrix

[sarah.ni68]

i want to form an equation with unknown coefficients, like u=c1*x^1+c2*x^2+...+cn*x^n
please help

 

[barry]

i want to form an equation with unknown coefficients, like u=c1*x^1+c2*x^2+...+cn*x^n

You just did.

Maybe you need to restate your question with a little more detail. Actually, with ANY detail.

 

[sarah.ni68]

You just did.

Maybe you need to restate your question with a little more detail. Actually, with ANY detail.

there is a differential equation that i want to solve it by using numerical method.. the differential equation is d²u/dx²-3*du/dx+2*u=0 u(0)=3, du/dx(0)=5
i want to assume an approximate response in form of u=c1*x^1+c2*x^2+...+cn*x^n+f0
f0=5*x+3 (according to the boundry conditions)
"n" is unknown, and will be inserted by user.
i think i should define a 1*n matrix of "c1" to "cn" coefficients: [c1 c2 ... cn], and a n*1 matrix of x^1...x^n: [x^1;x^2;...;x^n]
and then multiply these matrixes to create "u"
but because "n" is unknown, i can not define these matrixes!!