X三次方减去3X方加2加X=0RT

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X三次方减去3X方加2加X=0RT

X三次方减去3X方加2加X=0RT
X三次方减去3X方加2加X=0
RT

X三次方减去3X方加2加X=0RT
原式=x³-2x²-x²+x+2
=x²(x-2)-(x²-x-2)
=x²(x-2)-(x-2)(x+1)
=(x-2)(x²-x-1)

X³-3X²+2+X=0
(X-2)×(X²-X-1)=0
∴X²-X-1=0或X-2=0
∴X=2或X=(1+√5)/2或X=(1-√5)/2