4(y+7)=12; y=-4

asked by guest
on Jan 27, 2025 at 12:41 am



You asked:

Solve the system of equations:\[\begin{aligned}4 \left(y + 7\right) &= 12\\y &= -4\end{aligned}\]

MathBot Answer:

The system of equations has one solution.\[y = -4\]


Solve by Gauss-Jordan Elimination:

Begin by writing the augmented matrix of the system of equations. $$\begin{bmatrix}4 &\bigm |& -16\\1 &\bigm |& -4\end{bmatrix}$$

Then use a series of elementary row operations to convert the matrix into reduced-row echelon form. The three elementary row operations are:

  1. Swap the positions of any two rows.

  2. Multiply any row by a nonzero scalar.

  3. Multiply a row by a nonzero scalar and add it to any other row.


First, switch the rows in the matrix such that the row with the leftmost non-zero entry with the greatest magnitude is at the top.

$$\begin{bmatrix}4 &\bigm |& -16\\1 &\bigm |& -4\end{bmatrix}$$

Multiply row \(1\) by scalar \(\frac{1}{4}\) to make the leading term \(1\).

$$\begin{bmatrix}1 &\bigm |& -4\\1 &\bigm |& -4\end{bmatrix}$$

Multiply row \(1\) by scalar \(-1\) and add it to row \(2\).

$$\begin{bmatrix}1 &\bigm |& -4\\0 &\bigm |& 0\end{bmatrix}$$

Once the matrix is in reduced-row echelon form, convert the matrix back into linear equations to find the solution. $$\begin{aligned}1 \cdot y = -4 \\ y = -4\end{aligned}$$$$\begin{aligned}0 \cdot y = 0 \\ None = 0\end{aligned}$$