\sqrt{7} ,\\ 2,6< \sqrt{7} \\ |2,7- \sqrt{7} |-|2,6- \sqrt{7}|=2,7- \sqrt{7} -(\sqrt{7}-2,6)=\\=2,7- \sqrt{7} -\sqrt{7}+2,6=5,3-2 \sqrt{7}" alt="\sqrt{4 \pi^{2}-28\pi+49 }= \sqrt{ (2\pi-7)^{2}}=|2\pi-7|\\ 2\pi\approx6,28 \Rightarrow 2\pi<7 \Rightarrow |2\pi-7|=7-2\pi \\ \\ \sqrt{ (2,7- \sqrt{7} )^{2} } - \sqrt{ (2,6- \sqrt{7}) ^{2} } =|2,7- \sqrt{7} |-|2,6- \sqrt{7} |\\ 2,7> \sqrt{7} ,\\ 2,6< \sqrt{7} \\ |2,7- \sqrt{7} |-|2,6- \sqrt{7}|=2,7- \sqrt{7} -(\sqrt{7}-2,6)=\\=2,7- \sqrt{7} -\sqrt{7}+2,6=5,3-2 \sqrt{7}" align="absmiddle" class="latex-formula">