高等代数作业 第二章行列式答案

高等代数第四次作业

第二章 行列式 §1—§4

一、填空题

1.填上适当的数字,使72__43__1为奇排列. 6,5

2.四阶行列式D?aija11a213.设

a12a224?4中,含a24且带负号的项为_____. a11a24a33a42,a12a24a31a43,a13a24a32a41

a1n?a12a11n(n?1)a21?_____. (?1)2d ?a1n?a2na2n?a22?d.则

????????an1an2?annann?an2an1?1114.行列式1?1x的展开式中, x的系数是_____. 2 11?1二、判断题

1. 若行列式中有两行对应元素互为相反数,则行列式的值为0 ( )√

a11a12?a1na12a1na112. 设d=

a21a22?a2na22a2na21????则

=d( )×

an1an2?annan2annan1a11a12?a1na21a22?a2n3. 设d=

a21a22?a2n?????????则a??d( )×

n1an2?annan1an2?anna11a12?a1n000axyzaab4. 00bx?abcd ( ) √ xyb0000cyy 5.

xc00??abcd ( )×

6. 00dzzzd000007. 如果行列式D的元素都是整数,则D的值也是整数。( )√ 8. 如果行列D的元素都是自然数,则D的值也是自然数。( )×

a010?01002?09.

a2??a1a2?an ( )× 10. ?????=n!a000?n?1nn00?0三、选择题

cdefgh?0 ( xy ( )×

√ ) k211.行列式2k0?0的充分必要条件是 ( ) D

1?11(A)k?2 (B)k??2 (C)k?3 (D)k??2或 3

1xx22.方程124?0根的个数是( )C 139(A)0 (B)1 (C)2 (D)3 3.下列构成六阶行列式展开式的各项中,取“+”的有 ( )A

(A)a15a23a32a44a51a66 (B)a11a26a32a44a53a65 (C)a21a53a16a42a65a34 (D)a51a33a12a44a65a26 4. n阶行列式的展开式中,取“–”号的项有( )项 A

(A)n!2 (B)n22 (C)nn(n?1)2 (D)2

5.若(?1)?(1k4l5)a11ak2a43al4a55是五阶行列式的一项,则k,l的值及该项的符号为( )B

(A)k?2,l?3,符号为正; (B)k?2,l?3,符号为负; (C)k?3,l?1,符号为正; (D)k?1,l?3,符号为负

a11a12a132a112a122a136.如果D?a21a22a23?M?0,则D1?2a212a222a23 = ( )C

a31a32a332a312a322a33(A)2 M (B)-2 M (C)8 M (D)-8 M a11a12a134a112a11?3a122a137.如果D?a21a22a23?1,D1?4a212a21?3a222a23 ,则D1? ( )C

a31a32a334a312a31?3a322a33(A)8 (B)?12 (C)?24 (D)24

四、计算题

12341. 计算

23413412 41231234111111111111111解:

234134101212?10123412?1023412?10?101?2?1?10000?40?1000?4412341230?3?2?1004?400031112. 计算

13111131.

1113311111111111解:1311=6?1311020011311131=6?002=6?230?48. 1113111300021?10=160

?4高等代数第五次作业

第二章 行列式 §5—§7

一、填空题

1. 设Mij,Aij分别是行列式D中元素aij的余子式,代数余子式,则Mi,i?1?Ai,i?1?_____. 0

?30403 中元素3的代数余子式是 .?6 2. 52?21157811113. 设行列式D?,设M4j,A4j分布是元素a4j的余子式和代数余子式,

20361234则A41?A42?A43?A44 = ,M41?M42?M43?M44= .0,?66

?z?0?kx?4. 若方程组?2x?ky?z?0 仅有零解,则k . ?2

?kx?2y?z?0?5. 含有n个变量,n个方程的齐次线性方程组,当系数行列式D 时仅有零解. ?0 二、判断题

1. 若n级行列试D中等于零的元素的个数大于n2?n,则D=0 ( )√

002.

baca4.

acab6.

cd00abacca00efba00ddbb00ghab?(b2?a2)2 ( )√ 3. 00bb?0 ( )√ 5. dd00 7. ?a(gy?hx) ( )×

xyab003111ba001311113100ab00?(a2?b2)2 ( )√ ba11?48 ( )√ 1312345678?0 ( )√

111110?3?7?10三、选择题

1231. 行列式112的代数余子式A13的值是( )D

201

(A)3 (B)?1 (C)1 (D)?2 2.下列n(n >2)阶行列式的值必为零的是 ( )D

(A)行列式主对角线上的元素全为零 (B)行列式主对角线上有一个元素为零 (C)行列式零元素的个数多于n个 (D)行列式非零元素的个数小于n个

?10x13.若f(x)?11?1?11?11?1,则f(x)中x的一次项系数是( )D

1?1?11(A)1 (B)?1 (C)4 (D)?4

a100b14.4阶行列式

0a2b200b3a30 的值等于( )D b400a4(A)a1a2a3a4?b1b2b3b4 (B)(a1a2?b1b2)(a3a4?b3b4) (C)a1a2a3a4?b1b2b3b4 (D)(a2a3?b2b3)(a1a4?b1b4) 5.如果

a11a12?1,则方程组 ??a11x1?a12x2?b1?0a?a 的解是( )B 21a2221x1?a22x2?b2?0(A)xb1a121?b2a,xb12?a11(B)xb1a12a11b11??22a 21b2b2a,x2?22a21b 2(C)x?b1?a12?b1?a12?a11?b11??b??a11?b1 (D)x1?,x2??

2?a,x222?a21?b2?b2?a22?a21?b26. 三阶行列式第3行的元素为4,3,2对应的余子式分别为2,3,4,那么该行列式的值等于( (A)3 (B)7 (C)–3 (D)-7

?7.如果方程组 ?3x?ky?z?0?4y?z?0 有非零解,则 k =( )C ??kx?5y?z?0(A)0 (B)1 (C)-1 (D)3 四、计算题

a1001. 计算D=

?1a100?1a1 00?1aa100r0解:方法1:

?1a101?r?2?1a10a100r?1a12?ar101?a2a00?1a10?1a1?

0?1a1 00?1a00?1a00?1ar2?r3?1a10?1a

?0?1a1r?a2)r103?(1201?a2a0?0?1a100a3?2a1?a2 00?1a00?1aa3?2a1?a2=?1a=a(a3?2a)?(1?a2)?a4?3a2?1.

方法2:将行列式按第一行展开,有:

)B

a10?1a10a10?110a1?110=a?1a1?0a1=a[a??]?a2?1

0?1a1?1a0a00?1a0?1a0?1a =a[a(a2?1)?a]?a2?1?a4?3a2?1.

123?n234?12. 计算Dn?345?2

????n12?n?1123?n12n(n?1)23?n123?234?112n(n?1)34?1134?解:345?2?112n(n?1)45?2?2n(n?1)145????????????n12?n?112n(n?1)12?n?1112?123?n011?1?n1?1?12n(n?1)011?1?12n(n?1)1?1?n??????01?n1?11?n?11?1?1?10??n0n(n?1)n?12n(n?1)????(?1)212n(n?1) ?n?0011113. 计算

123414916

1827641111解:

123414916?(2?1)(3?1)(4?1)(3?2)(4?2)(4?3)?12

1827641?a1114. 计算D11?a21n?

111?an1?a1111?a11?01?a11解:D111?a2?0n?11?a2 ????+11?a2111?an11?an11n12 ?n?1?n1? 111

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