от math10.com » 14 Дек 2013, 13:58
1.[tex]\frac{x^2}{x^2-1}-\frac{x^2-1}{x^2}=\frac{3}{2} ; DM:x\ne \pm 1 , x\ne 0[/tex]
Полагаме [tex]\frac{x^2}{x^2-1}=t ; =>\frac{x^2-1}{x^2}=\frac{1}{t}[/tex]
[tex]t-\frac{1}{t}=\frac{3}{2}[/tex] Подвеждаме под общ знаменател и рационализираме
[tex]2t^2-3t-2=0[/tex]
[tex]D=9+16=25[/tex]
[tex]t_1=\frac{3+5}{4}=2 ; t_2=\frac{3-5}{2}=-\frac{1}{2}[/tex]
[tex]\frac{x^2}{x^2-1}=2 ; =>2x^2-2=x^2 ; =>x^2=2 ; =>x=\pm \sqrt{2}[/tex]
[tex]\frac{x^2}{x^2-1}=-\frac{1}{2} ; =>2x^2=-x^2+1 ; =>3x^2=1 ; =>x^2=\frac{1}{3} ; =>x=\pm \frac{\sqrt{3}}{3}[/tex]
2.[tex]\frac{2x-1}{x-1}=\frac{7x-1}{2(x+1)}[/tex]
[tex]\frac{2(x+1)(2x-1)}{2(x+1)(x-1)}=\frac{(7x-1)(x-1)}{2(x+1)(x-1)} ; DM: x\ne \pm 1[/tex]
[tex]2(x+1)(2x-1)=(7x-1)(x-1)[/tex]
[tex]4x^2+2x-2=7x^2-8x+1[/tex]
[tex]3x^2-10x+3=0[/tex]
[tex]D=100-36=64[/tex]
[tex]x_1=\frac{10+8}{6}=3 ; x_2=\frac{10-8}{6}=\frac{1}{3}[/tex]
3.[tex]\frac{4x+1}{2x-4}=\frac{x+2}{x-3}[/tex]
[tex]\frac{(4x+1)(x-3)}{2(x-2)(x-3)}=\frac{2(x-2)(x+2)}{2(x-2)(x-3)} ; DM: x\ne2 , x\ne \ne[/tex]
[tex](4x+1)(x-3)=2(x-2)(x+2)[/tex]
[tex]4x^2-11x-3=2x^2-8[/tex]
[tex]2x^2-11x+5=0[/tex]
[tex]D=121-40=81[/tex]
[tex]x_1=\frac{11+9}{4}=5 ; x_2=\frac{11-9}{4}=\frac{1}{2}[/tex]