下列方程:①3x^2+1=0 ②根号2x^2-根号3x+1=0

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下列方程:①3x^2+1=0②根号2x^2-根号3x+1=0下列方程:①3x^2+1=0②根号2x^2-根号3x+1=0下列方程:①3x^2+1=0②根号2x^2-根号3x+1=01①,②都是故选B2

下列方程:①3x^2+1=0 ②根号2x^2-根号3x+1=0
下列方程:①3x^2+1=0 ②根号2x^2-根号3x+1=0

下列方程:①3x^2+1=0 ②根号2x^2-根号3x+1=0
1①,②都是
故选B
2 由题知
m^2-2m-1=0
n^2-2n-1=0
且m+n=-b/a=2
mn=-1
即m^2-2m=1
n^2-2n=1
即3m^2-n^2-8m+1
=3m^2-6m-n^2-2m+1
=3(m^2-2m)-n^2-2m+1
=3-n^2-2m+1
=-n^2-2m+4
=-n^2+2n-2n-2m+4
=-(n^2-2n)-2(m+n)+4
=-1-2×2+4
=-1

  1.   B

  2. D