Question

.....................

Answer 1

3.

$\sqrt{265^2 - 96^2} =\sqrt{(265 - 96) (265 + 96)} =\sqrt{169*361} =13*19=247$

2.

$x^2-17x+42=0\\x^2+14x-51  \neq 0$

Получается

х=14

1.

$54-14\sqrt{5} =(7-\sqrt{5} )^2\\86+18\sqrt{5} =(9+\sqrt{5} ^2)[tex]\sqrt{54-14\sqrt{5}} +\sqrt{86+18\sqrt{5}} =16$\\[/tex]