x + y - 4z = 1
4x + y + 7z = -1
6x + y - z = 5
Multiply the first equation by -4, add to the second equation and replace the second by the result.
Multiply the first equation by -6, add to the third equation and replace the third by the result.
x + y - 4z = 1
-3y + 23z = -5
-5y + 23z = -1
Subtract the third equation from the second and replace the third equation by the result.
x + y - 4z = 1
-3y + 23z = -5
2y = -4
So, y = -2. Back substitute to get z = -11/23 and x = 25/23.
James S.
05/13/24