Đại số tuyến tính Ví dụ
[434112302]⎡⎢⎣434112302⎤⎥⎦
Bước 1
Bước 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.
Bước 1.1.1
Consider the corresponding sign chart.
|+-+-+-+-+|∣∣
∣∣+−+−+−+−+∣∣
∣∣
Bước 1.1.2
The cofactor is the minor with the sign changed if the indices match a -− position on the sign chart.
Bước 1.1.3
The minor for a12a12 is the determinant with row 11 and column 22 deleted.
|1232|∣∣∣1232∣∣∣
Bước 1.1.4
Multiply element a12a12 by its cofactor.
-3|1232|−3∣∣∣1232∣∣∣
Bước 1.1.5
The minor for a22a22 is the determinant with row 22 and column 22 deleted.
|4432|∣∣∣4432∣∣∣
Bước 1.1.6
Multiply element a22a22 by its cofactor.
1|4432|1∣∣∣4432∣∣∣
Bước 1.1.7
The minor for a32a32 is the determinant with row 33 and column 22 deleted.
|4412|∣∣∣4412∣∣∣
Bước 1.1.8
Multiply element a32a32 by its cofactor.
0|4412|0∣∣∣4412∣∣∣
Bước 1.1.9
Add the terms together.
-3|1232|+1|4432|+0|4412|−3∣∣∣1232∣∣∣+1∣∣∣4432∣∣∣+0∣∣∣4412∣∣∣
-3|1232|+1|4432|+0|4412|−3∣∣∣1232∣∣∣+1∣∣∣4432∣∣∣+0∣∣∣4412∣∣∣
Bước 1.2
Nhân 00 với |4412|∣∣∣4412∣∣∣.
-3|1232|+1|4432|+0−3∣∣∣1232∣∣∣+1∣∣∣4432∣∣∣+0
Bước 1.3
Tính |1232|∣∣∣1232∣∣∣.
Bước 1.3.1
Có thể tìm được định thức của một 2×22×2 ma trận bằng công thức |abcd|=ad-cb∣∣∣abcd∣∣∣=ad−cb.
-3(1⋅2-3⋅2)+1|4432|+0−3(1⋅2−3⋅2)+1∣∣∣4432∣∣∣+0
Bước 1.3.2
Rút gọn định thức.
Bước 1.3.2.1
Rút gọn mỗi số hạng.
Bước 1.3.2.1.1
Nhân 22 với 11.
-3(2-3⋅2)+1|4432|+0−3(2−3⋅2)+1∣∣∣4432∣∣∣+0
Bước 1.3.2.1.2
Nhân -3−3 với 22.
-3(2-6)+1|4432|+0−3(2−6)+1∣∣∣4432∣∣∣+0
-3(2-6)+1|4432|+0−3(2−6)+1∣∣∣4432∣∣∣+0
Bước 1.3.2.2
Trừ 66 khỏi 22.
-3⋅-4+1|4432|+0−3⋅−4+1∣∣∣4432∣∣∣+0
-3⋅-4+1|4432|+0−3⋅−4+1∣∣∣4432∣∣∣+0
-3⋅-4+1|4432|+0−3⋅−4+1∣∣∣4432∣∣∣+0
Bước 1.4
Tính |4432|∣∣∣4432∣∣∣.
Bước 1.4.1
Có thể tìm được định thức của một 2×22×2 ma trận bằng công thức |abcd|=ad-cb∣∣∣abcd∣∣∣=ad−cb.
-3⋅-4+1(4⋅2-3⋅4)+0−3⋅−4+1(4⋅2−3⋅4)+0
Bước 1.4.2
Rút gọn định thức.
Bước 1.4.2.1
Rút gọn mỗi số hạng.
Bước 1.4.2.1.1
Nhân 44 với 22.
-3⋅-4+1(8-3⋅4)+0−3⋅−4+1(8−3⋅4)+0
Bước 1.4.2.1.2
Nhân -3−3 với 44.
-3⋅-4+1(8-12)+0−3⋅−4+1(8−12)+0
-3⋅-4+1(8-12)+0−3⋅−4+1(8−12)+0
Bước 1.4.2.2
Trừ 1212 khỏi 88.
-3⋅-4+1⋅-4+0−3⋅−4+1⋅−4+0
-3⋅-4+1⋅-4+0−3⋅−4+1⋅−4+0
-3⋅-4+1⋅-4+0−3⋅−4+1⋅−4+0
Bước 1.5
Rút gọn định thức.
Bước 1.5.1
Rút gọn mỗi số hạng.
Bước 1.5.1.1
Nhân -3−3 với -4−4.
12+1⋅-4+012+1⋅−4+0
Bước 1.5.1.2
Nhân -4−4 với 11.
12-4+012−4+0
12-4+012−4+0
Bước 1.5.2
Trừ 44 khỏi 1212.
8+08+0
Bước 1.5.3
Cộng 88 và 00.
88
88
88
Bước 2
Since the determinant is non-zero, the inverse exists.
Bước 3
Set up a 3×63×6 matrix where the left half is the original matrix and the right half is its identity matrix.
[434100112010302001]⎡⎢⎣434100112010302001⎤⎥⎦
Bước 4
Bước 4.1
Multiply each element of R1R1 by 1414 to make the entry at 1,11,1 a 11.
Bước 4.1.1
Multiply each element of R1R1 by 1414 to make the entry at 1,11,1 a 11.
[443444140404112010302001]⎡⎢
⎢⎣443444140404112010302001⎤⎥
⎥⎦
Bước 4.1.2
Rút gọn R1R1.
[13411400112010302001]⎡⎢
⎢⎣13411400112010302001⎤⎥
⎥⎦
[13411400112010302001]⎡⎢
⎢⎣13411400112010302001⎤⎥
⎥⎦
Bước 4.2
Perform the row operation R2=R2-R1R2=R2−R1 to make the entry at 2,12,1 a 00.
Bước 4.2.1
Perform the row operation R2=R2-R1R2=R2−R1 to make the entry at 2,12,1 a 00.
[134114001-11-342-10-141-00-0302001]⎡⎢
⎢⎣134114001−11−342−10−141−00−0302001⎤⎥
⎥⎦
Bước 4.2.2
Rút gọn R2R2.
[134114000141-1410302001]⎡⎢
⎢⎣134114000141−1410302001⎤⎥
⎥⎦
[134114000141-1410302001]⎡⎢
⎢⎣134114000141−1410302001⎤⎥
⎥⎦
Bước 4.3
Perform the row operation R3=R3-3R1R3=R3−3R1 to make the entry at 3,13,1 a 00.
Bước 4.3.1
Perform the row operation R3=R3-3R1R3=R3−3R1 to make the entry at 3,13,1 a 00.
[134114000141-14103-3⋅10-3(34)2-3⋅10-3(14)0-3⋅01-3⋅0]⎡⎢
⎢
⎢
⎢⎣134114000141−14103−3⋅10−3(34)2−3⋅10−3(14)0−3⋅01−3⋅0⎤⎥
⎥
⎥
⎥⎦
Bước 4.3.2
Rút gọn R3R3.
[134114000141-14100-94-1-3401]⎡⎢
⎢
⎢⎣134114000141−14100−94−1−3401⎤⎥
⎥
⎥⎦
[134114000141-14100-94-1-3401]⎡⎢
⎢
⎢⎣134114000141−14100−94−1−3401⎤⎥
⎥
⎥⎦
Bước 4.4
Multiply each element of R2R2 by 44 to make the entry at 2,22,2 a 11.
Bước 4.4.1
Multiply each element of R2R2 by 44 to make the entry at 2,22,2 a 11.
[134114004⋅04(14)4⋅14(-14)4⋅14⋅00-94-1-3401]⎡⎢
⎢
⎢⎣134114004⋅04(14)4⋅14(−14)4⋅14⋅00−94−1−3401⎤⎥
⎥
⎥⎦
Bước 4.4.2
Rút gọn R2R2.
[13411400014-1400-94-1-3401]⎡⎢
⎢⎣13411400014−1400−94−1−3401⎤⎥
⎥⎦
[13411400014-1400-94-1-3401]⎡⎢
⎢⎣13411400014−1400−94−1−3401⎤⎥
⎥⎦
Bước 4.5
Perform the row operation R3=R3+94R2R3=R3+94R2 to make the entry at 3,23,2 a 00.
Bước 4.5.1
Perform the row operation R3=R3+94R2R3=R3+94R2 to make the entry at 3,23,2 a 00.
[13411400014-1400+94⋅0-94+94⋅1-1+94⋅4-34+94⋅-10+94⋅41+94⋅0]⎡⎢
⎢⎣13411400014−1400+94⋅0−94+94⋅1−1+94⋅4−34+94⋅−10+94⋅41+94⋅0⎤⎥
⎥⎦
Bước 4.5.2
Rút gọn R3R3.
[13411400014-140008-391]⎡⎢
⎢⎣13411400014−140008−391⎤⎥
⎥⎦
[13411400014-140008-391]⎡⎢
⎢⎣13411400014−140008−391⎤⎥
⎥⎦
Bước 4.6
Multiply each element of R3R3 by 1818 to make the entry at 3,33,3 a 11.
Bước 4.6.1
Multiply each element of R3R3 by 1818 to make the entry at 3,33,3 a 11.
[13411400014-140080888-389818]⎡⎢
⎢⎣13411400014−140080888−389818⎤⎥
⎥⎦
Bước 4.6.2
Rút gọn R3R3.
[13411400014-140001-389818]⎡⎢
⎢⎣13411400014−140001−389818⎤⎥
⎥⎦
[13411400014-140001-389818]⎡⎢
⎢⎣13411400014−140001−389818⎤⎥
⎥⎦
Bước 4.7
Perform the row operation R2=R2-4R3R2=R2−4R3 to make the entry at 2,32,3 a 00.
Bước 4.7.1
Perform the row operation R2=R2-4R3R2=R2−4R3 to make the entry at 2,32,3 a 00.
[134114000-4⋅01-4⋅04-4⋅1-1-4(-38)4-4(98)0-4(18)001-389818]⎡⎢
⎢
⎢
⎢⎣134114000−4⋅01−4⋅04−4⋅1−1−4(−38)4−4(98)0−4(18)001−389818⎤⎥
⎥
⎥
⎥⎦
Bước 4.7.2
Rút gọn R2R2.
[1341140001012-12-12001-389818]⎡⎢
⎢
⎢⎣1341140001012−12−12001−389818⎤⎥
⎥
⎥⎦
[1341140001012-12-12001-389818]⎡⎢
⎢
⎢⎣1341140001012−12−12001−389818⎤⎥
⎥
⎥⎦
Bước 4.8
Perform the row operation R1=R1-R3R1=R1−R3 to make the entry at 1,31,3 a 00.
Bước 4.8.1
Perform the row operation R1=R1-R3R1=R1−R3 to make the entry at 1,31,3 a 00.
[1-034-01-114+380-980-1801012-12-12001-389818]⎡⎢
⎢
⎢⎣1−034−01−114+380−980−1801012−12−12001−389818⎤⎥
⎥
⎥⎦
Bước 4.8.2
Rút gọn R1R1.
[134058-98-1801012-12-12001-389818]⎡⎢
⎢
⎢⎣134058−98−1801012−12−12001−389818⎤⎥
⎥
⎥⎦
[134058-98-1801012-12-12001-389818]⎡⎢
⎢
⎢⎣134058−98−1801012−12−12001−389818⎤⎥
⎥
⎥⎦
Bước 4.9
Perform the row operation R1=R1-34R2R1=R1−34R2 to make the entry at 1,21,2 a 00.
Bước 4.9.1
Perform the row operation R1=R1-34R2R1=R1−34R2 to make the entry at 1,21,2 a 00.
[1-34⋅034-34⋅10-34⋅058-34⋅12-98-34(-12)-18-34(-12)01012-12-12001-389818]⎡⎢
⎢
⎢⎣1−34⋅034−34⋅10−34⋅058−34⋅12−98−34(−12)−18−34(−12)01012−12−12001−389818⎤⎥
⎥
⎥⎦
Bước 4.9.2
Rút gọn R1R1.
[10014-341401012-12-12001-389818]⎡⎢
⎢
⎢⎣10014−341401012−12−12001−389818⎤⎥
⎥
⎥⎦
[10014-341401012-12-12001-389818]⎡⎢
⎢
⎢⎣10014−341401012−12−12001−389818⎤⎥
⎥
⎥⎦
[10014-341401012-12-12001-389818]⎡⎢
⎢
⎢⎣10014−341401012−12−12001−389818⎤⎥
⎥
⎥⎦
Bước 5
The right half of the reduced row echelon form is the inverse.
[14-341412-12-12-389818]⎡⎢
⎢
⎢⎣14−341412−12−12−389818⎤⎥
⎥
⎥⎦