x²+3x+1=0 则代数式1/x²+x²的值是
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x²+3x+1=0 则代数式1/x²+x²的值是
x²+3x+1=0 则代数式1/x²+x²的值是
x²+3x+1=0 则代数式1/x²+x²的值是
由x²+3x+1=0=>x²+1=-3x
∴
1/x²+x²=(x^4+1)/x²=[(x²+1)²-2x²]/x²
=[(-3x)²-2x²]/x²=7