用消元法解下列线性方程组：[tex=13.214x6.357]fnpmC2J6JmQBLyo5NmGAz6zmeLJinFI5/phsgBkpXmkn3/B5VAzrRtjteyV2asoZFKOTv+TehIAUmEU3vnw19arTbxGtEwXLul/ojrbHJjDebKRIX3y9TdU2SuIrQXhzkygHr220riYNXAyAloXe0veZagKUS7gE0wya0JvQGfPBxCBBqEgPLb2F3FK78cw6IaXYc4NBKyJ3MmQjpAZKSfPnDxQCqaEHsOd1kj4NNGdCEL9y8k3kJTdSlGKTf+CKMw2ory7DmBN/Hh3V+VN+Vr6g3JBuweViF9Tay+5zqB3GwLoa6YKXk1VbJLl+3BOk[/tex]

 用消元法解下列线性方程组 [tex=13.214x6.357]fnpmC2J6JmQBLyo5NmGAz6zmeLJinFI5/phsgBkpXmm8SYHQtgry6plRJsOC1FNdeKbV/z6KNiTiohnHmNanQ0ZdImJc30l30vXiB671zhPHTrw+Ybbf6kISmeMj3NpO9/AHIddT7gBX3TarikcJUEqEOPK8RGLvoYkPlbyszIB4Uty40Mlusw6YSiXF9stGBae064NkhejZUDXpzYzNW3z3GeSG0Og+kOetKo6U3MnJWjrW0NBl8MWPhRlzBnXZCQHg3zBFxO4/oRLkZrpav3VkFAjw4zmCD436r77XL03DbvU3S4E8CvNZ/Ejhzh1T[/tex]

用导出组的基础解系表出题中线性方程组的全部解，其中[tex=13.214x6.357]fnpmC2J6JmQBLyo5NmGAz6zmeLJinFI5/phsgBkpXmkn3/B5VAzrRtjteyV2asoZFKOTv+TehIAUmEU3vnw19arTbxGtEwXLul/ojrbHJjDebKRIX3y9TdU2SuIrQXhzkygHr220riYNXAyAloXe0veZagKUS7gE0wya0JvQGfN786ag69KDc5boprjYBYTArZylL7DFAlnJD4TgmeTUWktfEmZEKap6+R+JNqq5BoohFBjhbOyhY+EIbqmZmNfTwuMigJXK9YAZ0tjkmS0Z6DcJ2CAH2tCg55EotAzewFQqko4tLWBNAkjau5iCY8NK[/tex]

求线性方程组[tex=13.214x6.357]7EJHVCtO2IWq3KpdB+jQsrHCl3oODFt5CmjMvg8cZX/v9gklP+E2RRWz2G4AS8brK27NC/34uQHlMfNytX43g9Wnb+j2kkox2Cb9sNXEWqgHJ8iTKYZyauLHqm7Og1SWRi0x/k5E/JwKGB0mIHciVxnTREsEa+LDnXvSj/I1bJexotZqW2//WSr/nK/IsraiVC/Q9R4ER+y3x4zwbwaliqw5t9IRdMnGYeE7rRPygoNEMjlDjTca5ryHAr6GDDqMYOHZmU+YwP9EUoKlc2rVsYb+nb9sAlvX5uAR4bktLVeOYO+YC4xmdEMN2lt6WqPo[/tex]的全部解，并用对应导出组的基础解系表示.

下列变量组（）是一个闭回路。 A: {x，x，x，x，x，x} B: {x，x，x，x，x} C: {x，x，x，x，x，x} D: {x，x，x，x，x，x}

以下谓词蕴含式正确的是（）: (∀x) (A(x)→B(x))=>( ∀x)A(x)→(∀x)B(x)|(∀x) (A(x)↔B(x))=>( ∀x)A(x)↔(∀x)B(x)|(∀x)A(x)∨(∀x)B(x)=>( ∀x) (A(x)∨B(x))|(∃x) (A(x)∧B(x))=>(∃x)A(x)∧(∃x)B(x)

以下谓词蕴含式正确的是（）: (?x) (A(x)→B(x))=>( ?x)A(x)→(?x)B(x)|(?x) (A(x)?B(x))=>( ?x)A(x)?(?x)B(x)|(?x)A(x)∨(?x)B(x)=>( ?x) (A(x)∨B(x))|(?x) (A(x)∧B(x))=>(?x)A(x)∧(?x)B(x)

下列式中错误的是： A: (∀x)(A(x)Úp(x)) Û (∀x)A(x)Ú (∀x)p(x) B: ($x)A(x) Ù p Û ($x)(A(x) Ù p ) C: (∀x)(A(x)ÚB(x)) Þ (∀x)A(x)Ú( ∀x)B(x) D: ($x)(A(x)ÙB(x)) Þ ($x)A(x)Ù( $x)B(x)

判断下列推证是否正确。 (∀x)(A(x)→B(x))⇔(∀x)(￢A(x)∨B(x)) ⇔(∀x)￢( A(x)∧￢B(x) ) ⇔￢(∃x) ( A(x)∧￢B(x) ) ⇔￢( (∃x)A(x)∧(∃x)￢B(x) ) ⇔￢(∃x)A(x)∨￢(∃x)￢B(x) ⇔￢(∃x)A(x)∨(∀x)B(x) ⇔(∃x)A(x)→(∀x)B(x)

以下谓词公式中，( )不是逻辑有效式。 A: ($x)(P(x)∧Q(x)) Þ ($x) P(x)∧($x) Q(x) B: ("x)(P(x)∧Q(x)) Þ ("x) P(x)∧("x) Q(x) C: ($x)(P(x)∧Q(x)) Û ($x) P(x)∧($x) Q(x) D: ("x)(P(x)∧Q(x)) Û ("x) P(x)∧("x) Q(x)