1. **State the problem:** Solve the system of equations using elimination:
$$-4x - 9y = 26$$
$$8x + 9y = -34$$
2. **Add to eliminate y:** Adding the two equations cancels out $y$ because $-9y + 9y = 0$:
$$(-4x - 9y) + (8x + 9y) = 26 + (-34)$$
$$-4x + 8x + \cancel{-9y} + \cancel{9y} = -8$$
$$4x = -8$$
3. **Solve for $x$:**
$$x = \frac{-8}{4} = -2$$
4. **Substitute $x = -2$ into one original equation to find $y$:** Using the first equation:
$$-4(-2) - 9y = 26$$
$$8 - 9y = 26$$
5. **Isolate $y$:**
$$-9y = 26 - 8$$
$$-9y = 18$$
6. **Solve for $y$:**
$$y = \frac{18}{-9} = -2$$
7. **Check by subtracting to eliminate $y$:**
Subtract second equation from first:
$$(-4x - 9y) - (8x + 9y) = 26 - (-34)$$
$$-4x - 9y - 8x - 9y = 26 + 34$$
$$-12x - 18y = 60$$
This does not eliminate $y$, so subtraction is not useful here.
8. **Add to eliminate $x$:**
Add equations:
$$(-4x - 9y) + (8x + 9y) = 26 + (-34)$$
$$4x + 0 = -8$$
Already done in step 2.
9. **Subtract to eliminate $x$:**
Subtract second from first:
$$(-4x - 9y) - (8x + 9y) = 26 - (-34)$$
$$-12x - 18y = 60$$
Does not eliminate $x$ alone.
**Final solution:**
$$x = -2, \quad y = -2$$
Elimination System D3Aaa3
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