1.1) [tex]=> (x-\frac{3x}{x+3})^2+\frac{6x^2}{x+3}=\frac{40}{3}[/tex]
=> [tex](\frac{x^2}{x+3})^2+\frac{6x^2}{x+3}-\frac{40}{3}=0[/tex]
=> .....
3) [tex]x^2-4+3\sqrt{x^2-4}+4=0[/tex]
3.2 ) [tex]A=(n-1)^2(n^4-16n^3-64n^2+32n+160)[/tex]'
+) n=1 => TM
+) n#1
Đặt [tex]n^4-16n^3-64n^2+32n+160=a^2[/tex]
Mà [tex]n^4-16n^3-64n^2+32n+160[/tex] chia 3 dưa 1 => Đặt [tex]a=3k+1[/tex]
=> [tex]n^4-16n^3-64n^2+32n+160=(3k+1)^2[/tex]
=> [tex](n+3)(n^3-19n^2-7n+53)=3k(k+2)[/tex]
Tới đây xét n=-3 tm, n#-3 loại