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# boundary conditions

## boundary conditions

(OP)
I'm trying to solve a problem purley symbolically, my boundary conditions for my equation is 0 and L.
quick example:
My equation is

v(x,c0,c1,c2,c3):= c0+c1*x+c2*x^2+c3*x^3

x:=0

v(x,c0,c1,c2,c3)-> c0

that works fine

my problem is I would like to evaluate this at x=L as well.

So I would like to see

x:=L

v(x,c0,c1,c2,c3)-> c0+c1*L+c2*L^2+c3*L^3

Will mathcad do this for me? And then can I subsequently assign that result to another variable?

thanks.

### RE: boundary conditions

No, you have four unknowns and two equations.  You need four equations for your four unknowns.

### RE: boundary conditions

(OP)
I've got other equations;

My main issue is substituting in the L. That was my question.
Can I set x=L and have it evaluate the function in terms of L.
Whenever I set x=L it just complains that L isn't defined. Well, I don't wanna define it.

### RE: boundary conditions

if you have 4 equations for the 4 unkowns, then you can use L as if it is a symbolloc constant so c0,c1,c2,c3 can be solved in terms of L.  Use Given and Find.

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