PHƯƠNG TRÌNH toán 8- phiền mọi người!

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nhuquynhdat

$x^5=x^4+x^3+x^2+x+2$

$\leftrightarrow x^5-x^4-x^3-x^2-x-2=0$

$\leftrightarrow x^5-2x^4+x^4-2x^3+x^3-2x^2+x^2-2x+x-2=0$

$\leftrightarrow (x-2)(x^4+x^3+x^2+x+1)=0$

Do $x^4+x^3+x^2+x+1=x^2(x^2+x+1)+(x^2+x+1)-x^2=(x^2+x+1)(x^2+1)-x^2 \ne 0$

$\to x-2=0 \to x=2$
 
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