1.) Solve the system by triangularizing the augmented matrix and using back substitution.
-x-y+z=1
x-y-4z=-7
4x+y+z=6
2.) Perform the indicated row operation, then write the new matrix.
-4 4 | 4
9 -6 | 5 -2R1+ R2 ---> R2
3.) Solve the system by triangularizing the augmented matrix and using back substitution. If the system is linearly dependent, give the solution in terms of a parameter.
-x+y+z=0
3x+2y+5z=18
15x+10y+25z=89