### Home > PC3 > Chapter 9 > Lesson 9.1.4 > Problem9-78

9-78.

​Represent each system of equations below with matrices. Solve the system in part (c)?

1. \begin{aligned}[t] p + 2q &= 7\\ 3p + 4q &= 11 \end{aligned}

$\begin{bmatrix}1&2\\?&4\end{bmatrix}\begin{bmatrix}p\\?\end{bmatrix}=\begin{bmatrix}?\\11\end{bmatrix}$

1. \begin{aligned}[t] 4m − 5n &= −2\\ {-}3m + 4n &= 9 \end{aligned}

1. \begin{aligned}[t] 4x − y + z &= −5\\ 2x + 2y + 3z &= 10\\ 5x − 2y + 6z &= 1 \end{aligned}

If $AX = B$, then $X = A^{−1}B$.

1. \begin{aligned}[t] 7w − 3x + 2z &= 41 \\ −2w + x − z &= −13 \\ 4w + y − 2z &= 12\\ x − 3z & = 1 \end{aligned}

Be sure to include 0s in your matrix where variables are "missing".