# Question:How to simplify equations under a certain condition?

## Question:How to simplify equations under a certain condition?

example.3.mwsometimes, the system differential equations contain many parameters, such as K[t],K[a],L[a],R[a],etc.

Now, we input these differential equations to maple,namely,deq:=[...,...,...,...], of course, this input procedure consume much time.

Using sys:=DiffEquation(deq,[inputvariables],[outputvariables]) and tf:=TransferFunction(sys) yield the system transfer function.

Come under analysis, I find that a parameter, L[a], which cases the relative effect on the system can be neglected, so, I can set L[a]=0 in the differential equations.But as you know, the number of equations are a lot,and it is not easy to select L[a] in these equations.

Is there any way to substitute L[a]=0 into the former equations automatically, for example, let L[a]=0 in the former equations deq:=[...,...,...,...], and yield equations which won't contain the L[a] terms again?

Thank you very much!

Best Regards!

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