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5.
若實係數多項式\(f(x)=x^4+(2-k^2)x^2-2k^2x+(1-k^2)\)且\(f(x)=0\)只有兩個相異實根,則\(k\)的範圍為   
[解答]
\(\displaystyle f(x)=(x^4+2x^2+1)-k^2(x^2+2x+1) \)
\(\displaystyle =(x^2+1)^2-(kx+k)^2 \)
\(\displaystyle =(x^2+kx+(k+1))(x^2-kx+(1-k)) \)
名豈文章著官應老病休飄飄何所似Essential isolated singularity

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