deletions | additions       diff --git a/documentclass_article_usepackage_amsmath_begin__.tex b/documentclass_article_usepackage_amsmath_begin__.tex  index 35eaaa0..ab0400a 100644  --- a/documentclass_article_usepackage_amsmath_begin__.tex  +++ b/documentclass_article_usepackage_amsmath_begin__.tex 
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Y=  \begin{bmatrix}  Y_{11} \\  Y_{12}& 4 & 5 & 6 & 7  \\ 3 & 3 & 3 & 6 & 3 Y_{21} \\  Y_{22}  \end{bmatrix}  \]