Solve the system using matrices. gaussian elimination with back-substitution or gauss-jordan elimination. x + 5y= 0 x + 6y + z = 1 2x - y - z= -21 the solution set is si

In augmented matrix form, the system is

Subtract row 1 from row 2, and subtract 2 times row 1 from row 3:

Add 11 times row 1 to row 3:

Divide through row 3 by 10:

Row 3 says . Substituting into row 2, we get . Substituting both into row 1, we get . So the solution is the single ordered triplet (-10, 2, -1).