Help me solve the system below?
回答 (3)
3x - 5y + 2z = -53 …… [1]
x - 7y - 4z = -37 …… [2]
5x + 9y + 2z = 57 …… [3]
[1] × 2: 6x - 10y + 4z = -106 …… [4]
[2] × 2: 10x + 18y + 4z = 114 …… [5]
[2] + [4]: 7x - 17y = -143 …… [6]
[2] + [5]: 11x + 11y = 77
x + y = 7
y = 7 - x …… [7]
Plug [7] into [6]: 7x - 17(7 - x) = -143
24x = -24
x = -1
Plug x = -1 into [7]: y = 7 - (-1)
y = 8
Plug x = -1 and y = 8 into [2]: (-1) - 7(8) - 4z = -37
-4z = 20
z = -5
Hence, (x, y, z) = (-1, 8, -5)
3x - 5y + 2z = -53
x - 7y - 4z = -37
5x + 9y + 2z = 57
Solution:
x = -1, y = 8, z = -5
3x - 5y + 2z = -53 and x - 7y - 4z = -37 and 5x + 9y + 2z = 57
Since the only coefficient of 1 we have is the "x" in the second equation, let's solve for that in terms of "y" and "z" so we can then substitute it into the other two equations:
x - 7y - 4z = -37
x = 7y + 4z - 37
3x - 5y + 2z = -53 and 5x + 9y + 2z = 57
3(7y + 4z - 37) - 5y + 2z = -53 and 5(7y + 4z - 37) + 9y + 2z = 57
21y + 12z - 111 - 5y + 2z = -53 and 35y + 20z - 185 + 9y + 2z = 57
16y + 14z - 111 = -53 and 44y + 22z - 185 = 57
16y + 14z = 58 and 44y + 22z = 242
The first equation can be divided by 2 and the second by 22 to simplify:
8y + 7z = 29 and 2y + z = 11
Now we can solve for "z" in terms of "y" in the second equation and substitute one more time:
2y + z = 11
z = 11 - 2y
8y + 7z = 29
8y + 7(11 - 2y) = 29
8y + 77 - 14y = 29
-6y + 77 = 29
-6y = -48
y = 8
Now we can start working back and solving for "z" and "x":
z = 11 - 2y
z = 11 - 2(8)
z = 11 - 16
z = -5
x = 7y + 4z - 37
x = 7(8) + 4(-5) - 37
x = 56 - 20 - 37
x = -1
The answer to this system of equations is:
x = -1, y = 8, and z = -5
收錄日期: 2021-04-24 08:01:43
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