Question

solve by elimination:
4x + 9y = 28
-4x - y = -28
(7,0)
(6,0)
(-7,0)

Explanation:

Step1: Add the two equations

Add the equations \(4x + 9y = 28\) and \(-4x - y = -28\) together.
\[

$$\begin{align*} (4x + 9y) + (-4x - y) &= 28 + (-28)\\ 4x + 9y - 4x - y &= 0\\ 8y &= 0 \end{align*}$$

\]

Step2: Solve for y

Divide both sides of \(8y = 0\) by 8.
\[
y = \frac{0}{8} = 0
\]

Step3: Substitute y into one equation

Substitute \(y = 0\) into the first equation \(4x + 9y = 28\).
\[
4x + 9(0) = 28\\
4x = 28
\]

Step4: Solve for x

Divide both sides of \(4x = 28\) by 4.
\[
x = \frac{28}{4} = 7
\]

Answer:

(7, 0)