[tex]\it | \sqrt{7} - 5 \sqrt{7} | : (- \sqrt{28}) = ? \\ \\ |x| \Rightarrow \begin{cases} x \ pt. \ x\ \textgreater \ 0 \\ 0 \ pt. \ x=0 \\ -x \ pt.\ x\ \textless \ 0 \end{cases} \\ \\ \it | \sqrt{7} - 5 \sqrt{7} | = |-4 \sqrt{7}| = -(-4 \sqrt{7}) = 4 \sqrt{7} \\ \\ 4 \sqrt{7} : (-2\sqrt{7} ) = -2[/tex]
