1. **State the problem:** Solve the system of equations algebraically:
$$x - 2y + 2 = 0$$
$$x^2 + y^2 = 40$$
2. **Express one variable in terms of the other:** From the first equation,
$$x - 2y + 2 = 0 \implies x = 2y - 2$$
3. **Substitute into the second equation:** Replace $x$ with $2y - 2$ in the circle equation:
$$ (2y - 2)^2 + y^2 = 40 $$
4. **Expand and simplify:**
$$ (2y - 2)^2 = 4y^2 - 8y + 4 $$
So,
$$ 4y^2 - 8y + 4 + y^2 = 40 $$
$$ 5y^2 - 8y + 4 = 40 $$
5. **Bring all terms to one side:**
$$ 5y^2 - 8y + 4 - 40 = 0 $$
$$ 5y^2 - 8y - 36 = 0 $$
6. **Solve the quadratic equation:** Use the quadratic formula
$$ y = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} $$
where $a=5$, $b=-8$, $c=-36$.
Calculate the discriminant:
$$ \Delta = (-8)^2 - 4 \times 5 \times (-36) = 64 + 720 = 784 $$
So,
$$ y = \frac{8 \pm \sqrt{784}}{10} = \frac{8 \pm 28}{10} $$
7. **Find the two values of $y$:**
- For $+$:
$$ y = \frac{8 + 28}{10} = \frac{36}{10} = 3.6 $$
- For $-$:
$$ y = \frac{8 - 28}{10} = \frac{-20}{10} = -2 $$
8. **Find corresponding $x$ values:** Recall $x = 2y - 2$.
- For $y=3.6$:
$$ x = 2(3.6) - 2 = 7.2 - 2 = 5.2 $$
- For $y=-2$:
$$ x = 2(-2) - 2 = -4 - 2 = -6 $$
9. **Final solutions:**
$$ (x,y) = (5.2, 3.6) \quad \text{and} \quad (-6, -2) $$
Solve System 477A22
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