Algèbre Exemples
[221431201]⎡⎢⎣221431201⎤⎥⎦
Étape 1
Étape 1.1
Choose the row or column with the most 00 elements. If there are no 00 elements choose any row or column. Multiply every element in column 22 by its cofactor and add.
Étape 1.1.1
Consider the corresponding sign chart.
|+-+-+-+-+|∣∣
∣∣+−+−+−+−+∣∣
∣∣
Étape 1.1.2
The cofactor is the minor with the sign changed if the indices match a -− position on the sign chart.
Étape 1.1.3
The minor for a12a12 is the determinant with row 11 and column 22 deleted.
|4121|∣∣∣4121∣∣∣
Étape 1.1.4
Multiply element a12a12 by its cofactor.
-2|4121|−2∣∣∣4121∣∣∣
Étape 1.1.5
The minor for a22a22 is the determinant with row 22 and column 22 deleted.
|2121|∣∣∣2121∣∣∣
Étape 1.1.6
Multiply element a22a22 by its cofactor.
3|2121|3∣∣∣2121∣∣∣
Étape 1.1.7
The minor for a32a32 is the determinant with row 33 and column 22 deleted.
|2141|∣∣∣2141∣∣∣
Étape 1.1.8
Multiply element a32a32 by its cofactor.
0|2141|0∣∣∣2141∣∣∣
Étape 1.1.9
Add the terms together.
-2|4121|+3|2121|+0|2141|−2∣∣∣4121∣∣∣+3∣∣∣2121∣∣∣+0∣∣∣2141∣∣∣
-2|4121|+3|2121|+0|2141|−2∣∣∣4121∣∣∣+3∣∣∣2121∣∣∣+0∣∣∣2141∣∣∣
Étape 1.2
Multipliez 00 par |2141|∣∣∣2141∣∣∣.
-2|4121|+3|2121|+0−2∣∣∣4121∣∣∣+3∣∣∣2121∣∣∣+0
Étape 1.3
Évaluez |4121|∣∣∣4121∣∣∣.
Étape 1.3.1
Le déterminant d’une matrice 2×22×2 peut être déterminé en utilisant la formule |abcd|=ad-cb∣∣∣abcd∣∣∣=ad−cb.
-2(4⋅1-2⋅1)+3|2121|+0−2(4⋅1−2⋅1)+3∣∣∣2121∣∣∣+0
Étape 1.3.2
Simplifiez le déterminant.
Étape 1.3.2.1
Simplifiez chaque terme.
Étape 1.3.2.1.1
Multipliez 44 par 11.
-2(4-2⋅1)+3|2121|+0−2(4−2⋅1)+3∣∣∣2121∣∣∣+0
Étape 1.3.2.1.2
Multipliez -2−2 par 11.
-2(4-2)+3|2121|+0−2(4−2)+3∣∣∣2121∣∣∣+0
-2(4-2)+3|2121|+0−2(4−2)+3∣∣∣2121∣∣∣+0
Étape 1.3.2.2
Soustrayez 22 de 44.
-2⋅2+3|2121|+0−2⋅2+3∣∣∣2121∣∣∣+0
-2⋅2+3|2121|+0−2⋅2+3∣∣∣2121∣∣∣+0
-2⋅2+3|2121|+0−2⋅2+3∣∣∣2121∣∣∣+0
Étape 1.4
Évaluez |2121|∣∣∣2121∣∣∣.
Étape 1.4.1
Le déterminant d’une matrice 2×22×2 peut être déterminé en utilisant la formule |abcd|=ad-cb∣∣∣abcd∣∣∣=ad−cb.
-2⋅2+3(2⋅1-2⋅1)+0−2⋅2+3(2⋅1−2⋅1)+0
Étape 1.4.2
Simplifiez le déterminant.
Étape 1.4.2.1
Simplifiez chaque terme.
Étape 1.4.2.1.1
Multipliez 22 par 11.
-2⋅2+3(2-2⋅1)+0−2⋅2+3(2−2⋅1)+0
Étape 1.4.2.1.2
Multipliez -2−2 par 11.
-2⋅2+3(2-2)+0−2⋅2+3(2−2)+0
-2⋅2+3(2-2)+0−2⋅2+3(2−2)+0
Étape 1.4.2.2
Soustrayez 22 de 22.
-2⋅2+3⋅0+0−2⋅2+3⋅0+0
-2⋅2+3⋅0+0−2⋅2+3⋅0+0
-2⋅2+3⋅0+0−2⋅2+3⋅0+0
Étape 1.5
Simplifiez le déterminant.
Étape 1.5.1
Simplifiez chaque terme.
Étape 1.5.1.1
Multipliez -2−2 par 22.
-4+3⋅0+0−4+3⋅0+0
Étape 1.5.1.2
Multipliez 33 par 00.
-4+0+0−4+0+0
-4+0+0−4+0+0
Étape 1.5.2
Additionnez -4−4 et 00.
-4+0−4+0
Étape 1.5.3
Additionnez -4−4 et 00.
-4−4
-4−4
-4−4
Étape 2
Since the determinant is non-zero, the inverse exists.
Étape 3
Set up a 3×63×6 matrix where the left half is the original matrix and the right half is its identity matrix.
[221100431010201001]⎡⎢⎣221100431010201001⎤⎥⎦
Étape 4
Étape 4.1
Multiply each element of R1R1 by 1212 to make the entry at 1,11,1 a 11.
Étape 4.1.1
Multiply each element of R1R1 by 1212 to make the entry at 1,11,1 a 11.
[222212120202431010201001]⎡⎢
⎢⎣222212120202431010201001⎤⎥
⎥⎦
Étape 4.1.2
Simplifiez R1R1.
[11121200431010201001]⎡⎢
⎢⎣11121200431010201001⎤⎥
⎥⎦
[11121200431010201001]⎡⎢
⎢⎣11121200431010201001⎤⎥
⎥⎦
Étape 4.2
Perform the row operation R2=R2-4R1R2=R2−4R1 to make the entry at 2,12,1 a 00.
Étape 4.2.1
Perform the row operation R2=R2-4R1R2=R2−4R1 to make the entry at 2,12,1 a 00.
[111212004-4⋅13-4⋅11-4(12)0-4(12)1-4⋅00-4⋅0201001]⎡⎢
⎢⎣111212004−4⋅13−4⋅11−4(12)0−4(12)1−4⋅00−4⋅0201001⎤⎥
⎥⎦
Étape 4.2.2
Simplifiez R2R2.
[111212000-1-1-210201001]⎡⎢
⎢⎣111212000−1−1−210201001⎤⎥
⎥⎦
[111212000-1-1-210201001]⎡⎢
⎢⎣111212000−1−1−210201001⎤⎥
⎥⎦
Étape 4.3
Perform the row operation R3=R3-2R1R3=R3−2R1 to make the entry at 3,13,1 a 00.
Étape 4.3.1
Perform the row operation R3=R3-2R1R3=R3−2R1 to make the entry at 3,13,1 a 00.
[111212000-1-1-2102-2⋅10-2⋅11-2(12)0-2(12)0-2⋅01-2⋅0]⎡⎢
⎢⎣111212000−1−1−2102−2⋅10−2⋅11−2(12)0−2(12)0−2⋅01−2⋅0⎤⎥
⎥⎦
Étape 4.3.2
Simplifiez R3R3.
[111212000-1-1-2100-20-101]⎡⎢
⎢⎣111212000−1−1−2100−20−101⎤⎥
⎥⎦
[111212000-1-1-2100-20-101]⎡⎢
⎢⎣111212000−1−1−2100−20−101⎤⎥
⎥⎦
Étape 4.4
Multiply each element of R2R2 by -1−1 to make the entry at 2,22,2 a 11.
Étape 4.4.1
Multiply each element of R2R2 by -1−1 to make the entry at 2,22,2 a 11.
[11121200-0--1--1--2-1⋅1-00-20-101]⎡⎢
⎢⎣11121200−0−−1−−1−−2−1⋅1−00−20−101⎤⎥
⎥⎦
Étape 4.4.2
Simplifiez R2R2.
[111212000112-100-20-101]⎡⎢
⎢⎣111212000112−100−20−101⎤⎥
⎥⎦
[111212000112-100-20-101]⎡⎢
⎢⎣111212000112−100−20−101⎤⎥
⎥⎦
Étape 4.5
Perform the row operation R3=R3+2R2R3=R3+2R2 to make the entry at 3,23,2 a 00.
Étape 4.5.1
Perform the row operation R3=R3+2R2R3=R3+2R2 to make the entry at 3,23,2 a 00.
[111212000112-100+2⋅0-2+2⋅10+2⋅1-1+2⋅20+2⋅-11+2⋅0]⎡⎢
⎢⎣111212000112−100+2⋅0−2+2⋅10+2⋅1−1+2⋅20+2⋅−11+2⋅0⎤⎥
⎥⎦
Étape 4.5.2
Simplifiez R3R3.
[111212000112-100023-21]⎡⎢
⎢⎣111212000112−100023−21⎤⎥
⎥⎦
[111212000112-100023-21]⎡⎢
⎢⎣111212000112−100023−21⎤⎥
⎥⎦
Étape 4.6
Multiply each element of R3R3 by 1212 to make the entry at 3,33,3 a 11.
Étape 4.6.1
Multiply each element of R3R3 by 1212 to make the entry at 3,33,3 a 11.
[111212000112-1002022232-2212]⎡⎢
⎢⎣111212000112−1002022232−2212⎤⎥
⎥⎦
Étape 4.6.2
Simplifiez R3R3.
[111212000112-1000132-112]⎡⎢
⎢⎣111212000112−1000132−112⎤⎥
⎥⎦
[111212000112-1000132-112]⎡⎢
⎢⎣111212000112−1000132−112⎤⎥
⎥⎦
Étape 4.7
Perform the row operation R2=R2-R3R2=R2−R3 to make the entry at 2,32,3 a 00.
Étape 4.7.1
Perform the row operation R2=R2-R3R2=R2−R3 to make the entry at 2,32,3 a 00.
[111212000-01-01-12-32-1+10-1200132-112]⎡⎢
⎢
⎢⎣111212000−01−01−12−32−1+10−1200132−112⎤⎥
⎥
⎥⎦
Étape 4.7.2
Simplifiez R2R2.
[11121200010120-1200132-112]⎡⎢
⎢
⎢⎣11121200010120−1200132−112⎤⎥
⎥
⎥⎦
[11121200010120-1200132-112]⎡⎢
⎢
⎢⎣11121200010120−1200132−112⎤⎥
⎥
⎥⎦
Étape 4.8
Perform the row operation R1=R1-12R3R1=R1−12R3 to make the entry at 1,31,3 a 00.
Étape 4.8.1
Perform the row operation R1=R1-12R3R1=R1−12R3 to make the entry at 1,31,3 a 00.
[1-12⋅01-12⋅012-12⋅112-12⋅320-12⋅-10-12⋅12010120-1200132-112]⎡⎢
⎢
⎢⎣1−12⋅01−12⋅012−12⋅112−12⋅320−12⋅−10−12⋅12010120−1200132−112⎤⎥
⎥
⎥⎦
Étape 4.8.2
Simplifiez R1R1.
[110-1412-14010120-1200132-112]⎡⎢
⎢
⎢⎣110−1412−14010120−1200132−112⎤⎥
⎥
⎥⎦
[110-1412-14010120-1200132-112]⎡⎢
⎢
⎢⎣110−1412−14010120−1200132−112⎤⎥
⎥
⎥⎦
Étape 4.9
Perform the row operation R1=R1-R2R1=R1−R2 to make the entry at 1,21,2 a 00.
Étape 4.9.1
Perform the row operation R1=R1-R2R1=R1−R2 to make the entry at 1,21,2 a 00.
[1-01-10-0-14-1212-0-14+12010120-1200132-112]⎡⎢
⎢
⎢⎣1−01−10−0−14−1212−0−14+12010120−1200132−112⎤⎥
⎥
⎥⎦
Étape 4.9.2
Simplifiez R1.
[100-341214010120-1200132-112]
[100-341214010120-1200132-112]
[100-341214010120-1200132-112]
Étape 5
The right half of the reduced row echelon form is the inverse.
[-341214120-1232-112]