Question: Calculating an equation u(x,t) for all (x,t) from -infinity to infinity

Question:I've defined wave, but it's after that it gets sticky. This is my attempt:As you can see, not very fruitful. I have tried wave(x=-infinity..infinity, t=-infinity, infinity) which returns an error. 

When i sub in wave(1,1) i get an answer, or any other number for that matter, but I'm not sure how to actually aswer this question. 

Any and all help appreciated

Thank you

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