The matrix that reflects across the plane through the origin with unit normal $\mathbf{N} = (a,b,c)$ is:
$$
\mathbf{I} - 2\mathbf{N}^T\mathbf{N} =
\begin{bmatrix} 
{1- 2a^2} &amp;   {-2ab}  &amp;   {-2ac} \\
 {-2ab}   &amp;  {1-2b^2} &amp;   {-2bc} \\
 {-2ac}   &amp;   {-2bc}  &amp;  {1-2c^2}
\end{bmatrix}
$$
See here for reference. A normal of your plane is $\mathbf{N} = (-1,1,1)$, so plug in $a=-1/\sqrt{3}$, $b=1\sqrt{3}$, $c=1\sqrt{3}$.

Reflection across the plane
I am able to import my .csv file using Apex Data Loader. When I try importing the same file from CLI I am getting an exception attached in the file.
When the file contents are copied into a new csv file and try importing this new .csv file, this succeeds.
Also If I open my .csv file, click on save, a pop-up comes up "MyFile.csv may contain features that are not compatible with CSV(Comma Delimited).
Do you want to keep the workbook in this format? " And if I click on "Yes" or "No"and close the file without saving it and then try to upload the same file. 
The data gets uploaded.
This is something weird and I am not able to get any logic out of it..

This is the error msg i am getting.

