# Help here derivative question?

Prove that for every $x$, we have $\Delta[f(x)+g(x)]=\Delta f(x)+ \Delta g(x)$. Thanks in advance.

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What is $\Delta(f(x))$ for you? –  Sigur Nov 11 '12 at 13:43
Please, try to make the title of your question more informative. E.g., Why does $a<b$ imply $a+c<b+c$? is much more useful for other users than A question about inequality. From How can I ask a good question?: Make your title as descriptive as possible. In many cases one can actually phrase the title as the question, at least in such a way so as to be comprehensible to an expert reader. –  Julian Kuelshammer Nov 11 '12 at 13:44
The laplacian $\Delta$ is a linear differential operator. Don't you understand my answer? Well, try to explain what you are asking, please. –  Siminore Nov 11 '12 at 14:26
Since Notyathing said "derivative question", it's likely $\Delta$ is the Laplacian (or perhaps some other differential operator). It does not represent general differences as in your answer. –  Mark S. Nov 11 '12 at 15:50