Not return Value when using integral in MathCad Prime!!

Hi Every one

Can any body Help me about this problem?

I Have Attached main file which is done by MathCad Prime 4.0

This is distributed load on a simple support beam and "V" and "M" are shear and moment, regardless of what is physical meaning of this parameters just as a mathematics

I do not know why M(x) does not return any answer while I can take answer in MathCAD 15  with same formulas!!

I do not want to use Evaluate for first integral because it makes another problem when "a=0"

Thanks in Advance

Ramak

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