2.5÷0.7，商精确到千分位是（）。 A: 3.572 B: 3.571 C: 3.57

样木相关系数与回归系数的数量关系是 未知类型：{'options': ['[tex=3.571x2.286]6J/0uIyeesRxEtqG6DZ++3NQa2mbPje2wcTXpRt2jdrU6K1E0PxP1rfcJK9ZfNdA[/tex]', '[tex=3.571x2.429]6J/0uIyeesRxEtqG6DZ++9zpLiz5t23QvjsYNjDC8ahBmHSECV+QR0QYqk9QFuqS[/tex]', '[tex=3.571x2.286]kpkMvE3fgIEHqRVWHnmhU1g37EwQKcFHdqA1/pdcGx7wOsTezYLchapAbO/fJ5cu[/tex]', '[tex=4.571x2.214]dEgERHQyZeQFvawhwtE4k7vhDOhOrYkrk+cCKQltDWU=[/tex]'], 'type': 102}

求下列函数在孤立奇点处的留数（包括无穷远点）。（4）[tex=3.571x2.286]h3lfFE0p81SjiZLUH6GVu0Y4KwqeCD6MhDZ3AzcxjXU=[/tex] ；

如图所示,两无限大平行板,其电荷面密度为+σ,图中a,b,c三处的电场强度的大小分别为 未知类型：{'options': ['[tex=3.0x2.286]MXt3WVmWxsVirhIAkqgn72+gDJC3Sz8oIlJ1laErM5RErrKcKEU0oXapeOa1Agsw[/tex]', '[tex=3.571x2.286]m4BcqsUFsRjPRRpozvygmSAQjlH4a+Kv1ynoTwfGgRGd0xQz5sp7EDYZUOicAzJIl5TSqAdECROFSr1+cis5KwOTKnceaiAt4IobShHhc+c=[/tex]', '[tex=5.429x2.286]6tJ7NCCOiw8f49v33DWhjjaz6i64MztUZmKDPubck+Zj2pfUJQev2oRus5C8ijd73q5/4QcrfRLQ4M2696yjOtuIWU6cea5eBxcat5CUqs2ecUp4XI2zmaWbH4KSiSkXyzcKJ8RWm8hB5ixhmRHsag==[/tex]', '[tex=3.5x2.286]MXt3WVmWxsVirhIAkqgn73Fs24Nh+sqhClutem9wC9ax1fKhTQ6xgEJDcyIyUaS9[/tex]'], 'type': 102}

如图所示,两无限大平行板,其电荷面密度为+σ,图中a,b,c三处的电场强度的大小分别为 未知类型：{'options': ['[tex=3.0x2.286]MXt3WVmWxsVirhIAkqgn72+gDJC3Sz8oIlJ1laErM5RErrKcKEU0oXapeOa1Agsw[/tex]', '[tex=3.571x2.286]m4BcqsUFsRjPRRpozvygmSAQjlH4a+Kv1ynoTwfGgRGd0xQz5sp7EDYZUOicAzJIl5TSqAdECROFSr1+cis5KwOTKnceaiAt4IobShHhc+c=[/tex]', '[tex=5.429x2.286]6tJ7NCCOiw8f49v33DWhjjaz6i64MztUZmKDPubck+Zj2pfUJQev2oRus5C8ijd73q5/4QcrfRLQ4M2696yjOtuIWU6cea5eBxcat5CUqs2ecUp4XI2zmaWbH4KSiSkXyzcKJ8RWm8hB5ixhmRHsag==[/tex]', '[tex=3.5x2.286]MXt3WVmWxsVirhIAkqgn73Fs24Nh+sqhClutem9wC9ax1fKhTQ6xgEJDcyIyUaS9[/tex]'], 'type': 102}

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)