Solve.
-7x + 7y + z = 1 x + 8y + 8z = 8
9x + y + 9z = 9

Question

Quizplus · Accepted Answer

Rearranging the equations in matrix form, we get:
$\begin{bmatrix}
7 & 7 & 1\
1 & 8 & 8\
9 & 1 & 9
\end{bmatrix} \begin{bmatrix}
x\
y\
z
\end{bmatrix} = \begin{bmatrix}
1\
8\
9
\end{bmatrix}$
Now, finding the inverse of the $3	imes3$ matrix on the left, we get:
$\begin{bmatrix}
\frac{7}{8} & -\frac{7}{64} & -\frac{1}{32}\
-\frac{1}{8} & \frac{9}{64} & \frac{1}{32}\
-\frac{1}{8} & -\frac{1}{64} & \frac{9}{32}
\end{bmatrix} \begin{bmatrix}
1\
8\
9
\end{bmatrix} = \begin{bmatrix}
0\
0\
1
\end{bmatrix}$
Therefore, the solution is $x=0,y=0,z=1$, which corresponds to answer choice D.

Solve. -7x + 7y + Z = 1 X + 8y