Ответ:

Объяснение:

[tex]=(\frac{1}{\sqrt{b}-5 }-\frac{\sqrt{b} }{(\sqrt{b}-5)(\sqrt{b}+5) })*\frac{(\sqrt{b}-5)^2 }{5\sqrt{b} } -\frac{2}{\sqrt{b}+5 }=(\frac{\sqrt{b}+5-\sqrt{b} }{(\sqrt{b}-5)(\sqrt{b}+5)} )*\frac{(\sqrt{b}-5)^2 }{5\sqrt{b} } -\frac{2}{\sqrt{b}+5 }=\\ \frac{\sqrt{b}-5 }{\sqrt{b}(\sqrt{b}+5) } -\frac{2}{\sqrt{b}+5 }=\frac{\sqrt{b}-5-2\sqrt{b} }{\sqrt{b}(\sqrt{b}+5)}=\frac{-(\sqrt{b}+5) }{\sqrt{b}(\sqrt{b}+5)}= -\frac{1}{\sqrt{b} }[/tex]

[tex]-\frac{1}{\sqrt{\frac{16}{49} } }= -\frac{7}{4}= -1,75[/tex]