Show that | $\left\lVert x \right\rVert - \left\lVert y \right\rVert$ | $\leq$ $\left\lVert x - y \right\rVert$ for any x and y in a normed space.
Here is my attempt:
Take the triangle inequality \begin{align*} \left\lVert x + y \right\rVert &\leq \left\lVert x + y \right\rVert + \left\lVert y \right\rVert \\ &= \left\lVert x - y + y \right\rVert + \left\lVert y \right\rVert \\ &\leq \left\lVert x - y\right\rVert + \left\lVert y \right\rVert + \left\lVert y \right\rVert. \end{align*}
Then we move the two $\left\lVert y \right\rVert$'s to the other side \begin{align*} \left\lVert x-y \right\rVert &\geq \left\lVert x + y \right\rVert - \left\lVert y \right\rVert - \left\lVert y \right\rVert \\ &\geq \left\lVert x \right\rVert + \left\lVert y \right\rVert - \left\lVert y \right\rVert - \left\lVert y \right\rVert\\ &\geq \left\lVert x \right\rVert - \left\lVert y \right\rVert.\end{align*}
I am not sure if I can separate the $\left\lVert x + y \right\rVert$ into $\left\lVert x \right\rVert + \left\lVert y \right\rVert$ like I did and I am not sure how to get absolute values so any hints would be great.