Let u(x) and v(x) are functions of variable x: $\displaystyle \lim_{x\to a} u(x) = \lim_{x\to a} v(x) =0 $. We say that u(x)~v(x) if $\displaystyle \lim_{x\to a}\frac{u(x)}{v(x)} =1 $.

So, if we have u~u', v~v'; can we have u+v~u'+v'?

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