Question: How to Differentiate diff(x,t),taken diff(x,t) as a variable?

 

Friends, as above in the picture,I want T to differentiate diff(x,t),taken diff(x,t) as a variable.

The answer is m*diff(x,t)+m__1/2 

Is there any way to do that? Substitute diff(x,t) with another variable and then substitute back isn't convenient.

differential_question.mw

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