- #1
sara_87
- 763
- 0
Question:
solve by using gaussian elimination:
3x - y + z = 1
2x + 2y – 5z = 0
5x + y – 4z = 7
what i did:
step 1: new row 1 = old row 1 – row 2, I got:
x – 3y + 6z = 1
2x + 2y – 5z = 0
5x + y – 4z = 7
step 2: new row 2 = old row 2 – (2 * row1) and new row 3 = old row 3 – (5 * row 1), I got:
x – 3y + 6z = 1
0 + 8y – 17z = -2
0 + 16y – 34z = 2
step 3: new row 3 = old row 3 * (1/2) I got:
x – 3y + 6z = 1
0 + 8y – 17z = -2
0 + 8y – 16z = 1
step 4: new row 3 = old row 3 – row 2, I got:
x – 3y + 6z = 1
0 + 8y – 17z = -2
0 + 0 + z = 3
the Real Answer:
Gaussian elimination gives 0z = 6, ie, 0 = 6 which is clearly impossible.
NO solutions.
i obviously didn’t get that, and i would really appreciate it if someone could check whether i am going wrong somewhere or if my teacher is wrong
thanx
solve by using gaussian elimination:
3x - y + z = 1
2x + 2y – 5z = 0
5x + y – 4z = 7
what i did:
step 1: new row 1 = old row 1 – row 2, I got:
x – 3y + 6z = 1
2x + 2y – 5z = 0
5x + y – 4z = 7
step 2: new row 2 = old row 2 – (2 * row1) and new row 3 = old row 3 – (5 * row 1), I got:
x – 3y + 6z = 1
0 + 8y – 17z = -2
0 + 16y – 34z = 2
step 3: new row 3 = old row 3 * (1/2) I got:
x – 3y + 6z = 1
0 + 8y – 17z = -2
0 + 8y – 16z = 1
step 4: new row 3 = old row 3 – row 2, I got:
x – 3y + 6z = 1
0 + 8y – 17z = -2
0 + 0 + z = 3
the Real Answer:
Gaussian elimination gives 0z = 6, ie, 0 = 6 which is clearly impossible.
NO solutions.
i obviously didn’t get that, and i would really appreciate it if someone could check whether i am going wrong somewhere or if my teacher is wrong
thanx
Last edited: