1. **State the problem:** Kyle is adding the two equations:
$$4x - 2y = 18$$
$$-3x + 2y = -11$$
2. **Add the equations:** When adding, combine like terms:
$$ (4x - 3x) + (-2y + 2y) = 18 + (-11) $$
Simplify:
$$ x + 0 = 7 $$
So,
$$ x = 7 $$
3. **Answer for question 1:** The sum of the two equations is $x = 7$, which corresponds to option b.
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4. **State the problem:** Vivi wants to solve the system:
$$4x + 6y = -14$$
$$-x + 3y = -10$$
5. **Goal:** Use elimination to eliminate one variable by making coefficients opposites.
6. **Check options:**
- Multiply the 2nd equation by 2:
$$2(-x + 3y) = 2(-10) \\ -2x + 6y = -20$$
Now the system is:
$$4x + 6y = -14$$
$$-2x + 6y = -20$$
- Multiply the 2nd equation by -4:
$$-4(-x + 3y) = -4(-10) \\ 4x - 12y = 40$$
- Multiply the 2nd equation by 4:
$$4(-x + 3y) = 4(-10) \\ -4x + 12y = -40$$
7. **Conclusion:** Both multiplying by 2 and by 4 are valid first steps to create coefficients that can be eliminated. So option d (both a and c) is correct.
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8. **Solve system 3:**
$$-x + 5y = -29$$
$$2x - 5y = 38$$
Add the two equations:
$$(-x + 2x) + (5y - 5y) = -29 + 38$$
$$x + 0 = 9$$
$$x = 9$$
Substitute $x=9$ into first equation:
$$-9 + 5y = -29 \\ 5y = -20 \\ y = -4$$
Answer: $(9, -4)$
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9. **Solve system 4:**
$$3x + 3y = 21$$
$$-3x + 2y = 19$$
Add the two equations:
$$(3x - 3x) + (3y + 2y) = 21 + 19$$
$$0 + 5y = 40$$
$$5y = 40 \\ y = 8$$
Substitute $y=8$ into first equation:
$$3x + 3(8) = 21 \\ 3x + 24 = 21 \\ 3x = -3 \\ x = -1$$
Answer: $(-1, 8)$
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10. **Solve system 5:**
$$8x - 2y = -10$$
$$4x - y = -5$$
Multiply second equation by -2:
$$-2(4x - y) = -2(-5) \\ -8x + 2y = 10$$
Add to first equation:
$$(8x - 8x) + (-2y + 2y) = -10 + 10$$
$$0 = 0$$
This means the system has infinitely many solutions.
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11. **Solve system 6:**
$$3x - 5y = -9$$
$$2x + 2y = 10$$
Multiply second equation by 5:
$$5(2x + 2y) = 5(10) \\ 10x + 10y = 50$$
Multiply first equation by 2:
$$2(3x - 5y) = 2(-9) \\ 6x - 10y = -18$$
Add the two equations:
$$(6x + 10x) + (-10y + 10y) = -18 + 50$$
$$16x + 0 = 32 \\ 16x = 32 \\ x = 2$$
Substitute $x=2$ into second original equation:
$$2(2) + 2y = 10 \\ 4 + 2y = 10 \\ 2y = 6 \\ y = 3$$
Answer: $(2, 3)$
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12. **Solve system 7:**
$$3(4x - 6y) = 3(-2) \\ 12x - 18y = -6$$
$$-4(3x + 5y) = -4(8) \\ -12x - 20y = -32$$
Add the two equations:
$$(12x - 12x) + (-18y - 20y) = -6 + (-32)$$
$$0 - 38y = -38 \\ -38y = -38 \\ y = 1$$
Substitute $y=1$ into first equation:
$$12x - 18(1) = -6 \\ 12x - 18 = -6 \\ 12x = 12 \\ x = 1$$
Answer: $(1, 1)$
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**Summary of answers:**
1. b. $x=7$
2. d. Both a and c could work
3. $(9, -4)$
4. $(-1, 8)$
5. Infinitely many solutions
6. $(2, 3)$
7. $(1, 1)$
Systems Elimination
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