cho h/s [TEX]g= \sqrt{x+sqrt{1+x^2}}[/TEX]
[TEX]c/m 4(1+x^2).g"+4x.g'-g' =0[/TEX]
post lại cái đề
ta có [TEX]g'=\frac{(x+\sqrt{1+x^2})'}{2\sqrt{x+\sqrt{1+x^2}}}[/TEX]
[TEX]=\frac{1+\frac{x}{\sqrt{1+x^2}}}{2\sqrt{x+\sqrt{1+x^2}}}[/TEX]
[TEX]=\frac{\sqrt{1+x^2}+x}{2.\sqrt{1+x^2}.\sqrt{x+ \sqrt{ 1 +x^2}}}[/TEX]