6. Let real numbers $a, b$ satisfy the inequality $||a|-(a+b)|<|a-| a+b||$, then the positive and negative signs of $a, b$ are

保留了源文本的换行和格式。
Rong's matter is negative and positive.
Analysis From the given we get
$$
\begin{aligned}
{[|a|-(a+b)]^{2} } & 0 \Rightarrow b>-a>0, a \text{ is negative and } b \text{ is positive.}
\end{aligned}
$$