Tìm nghiệm đa thức đây?

V

vansang02121998

[tex]P(x)=-Q(x)[/tex]

[tex]\Leftrightarrow x^3+2x^2+x-1=x^3+x-3x-1[/tex]

[tex]\Leftrightarrow x^3+2x^2+x-1-x^3-x^2+3x+1=0[/tex]

[tex]\Leftrightarrow x^2+4x=0[/tex]

[tex]\Leftrightarrow x(x+4)=0[/tex]

[tex]\Leftrightarrow \left[\begin{x=0}\\{x = -4} [/tex]
 
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G

goku123123

Để P(x)=-Q(x)
=>x^3+2x^2+x-1=-(-x^3-x^2+3x+1)
=>x^3+2x^2+x-1=x^3+x^2-3x-1
=>(x^3-x^3)+(2x^2-x^2)+(x+3x)=-1+1
=>x^2+4x=0
=>x(x+4)=0
=>x=0 hoặc x=-4

:D
 
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