toan 8<img src="http://diendan.hocmai.vn/images/eyeeasy/buttons/ChuaXN.png" border="0">

K

kisihoangtoc

$x^4-x^3+2x^2-x+1$
$=x^2(x^2+1)-x(x^2+1)+(x^2+1)$
$=(x^2+1)(x^2-x+1)>0$
Vậy P có nghĩa với mọi x
$P=\frac{x^3+x^2+x+1}{x^4-x^3+2x^2-x+1}$
$=\frac{(x^2+1)(x+1)}{(x^2+1)(x^2-x+1)}$
$=\frac{x+1}{x^2-x+1}=2$
\Rightarrow $x+1=2(x^2-x+1)$
\Leftrightarrow $2x^2-3x+2=0$
\Leftrightarrow $(2x-1)(x-1)=0$
\Rightarrow $x=\frac{1}{2}$ hoặc $x=1$
 
You must log in or register to reply here.
Top Bottom