1. **State the problem:** Solve the simultaneous equations:
$$2x + 3y = 6$$
and
$$(2x + 1)^2 + y(y - 2)^2 = 49$$
2. **Use substitution:** From the first equation, express $x$ in terms of $y$:
$$2x = 6 - 3y \implies x = \frac{6 - 3y}{2}$$
3. **Substitute into the second equation:** Replace $x$ with $\frac{6 - 3y}{2}$:
$$\left(2\cdot \frac{6 - 3y}{2} + 1\right)^2 + y(y - 2)^2 = 49$$
Simplify inside the first term:
$$\left(6 - 3y + 1\right)^2 + y(y - 2)^2 = 49$$
$$\left(7 - 3y\right)^2 + y(y - 2)^2 = 49$$
4. **Expand the squares:**
$$ (7 - 3y)^2 = 49 - 42y + 9y^2 $$
$$ (y - 2)^2 = y^2 - 4y + 4 $$
So,
$$ y(y - 2)^2 = y(y^2 - 4y + 4) = y^3 - 4y^2 + 4y $$
5. **Rewrite the equation:**
$$ 49 - 42y + 9y^2 + y^3 - 4y^2 + 4y = 49 $$
6. **Simplify and bring all terms to one side:**
$$ y^3 + (9y^2 - 4y^2) + (-42y + 4y) + 49 - 49 = 0 $$
$$ y^3 + 5y^2 - 38y = 0 $$
7. **Factor the cubic:**
$$ y(y^2 + 5y - 38) = 0 $$
So either
$$ y = 0 $$
or solve quadratic
$$ y^2 + 5y - 38 = 0 $$
8. **Solve quadratic using formula:**
$$ y = \frac{-5 \pm \sqrt{5^2 - 4 \cdot 1 \cdot (-38)}}{2} = \frac{-5 \pm \sqrt{25 + 152}}{2} = \frac{-5 \pm \sqrt{177}}{2} $$
9. **Find corresponding $x$ values:**
- For $y=0$:
$$ x = \frac{6 - 3\cdot 0}{2} = 3 $$
- For $y = \frac{-5 + \sqrt{177}}{2}$:
$$ x = \frac{6 - 3y}{2} = \frac{6 - 3 \cdot \frac{-5 + \sqrt{177}}{2}}{2} = \frac{6 - \frac{-15 + 3\sqrt{177}}{2}}{2} = \frac{\frac{12 + 15 - 3\sqrt{177}}{2}}{2} = \frac{27 - 3\sqrt{177}}{4} $$
- For $y = \frac{-5 - \sqrt{177}}{2}$:
$$ x = \frac{6 - 3y}{2} = \frac{27 + 3\sqrt{177}}{4} $$
**Final solutions:**
$$ (x,y) = (3, 0), \left(\frac{27 - 3\sqrt{177}}{4}, \frac{-5 + \sqrt{177}}{2}\right), \left(\frac{27 + 3\sqrt{177}}{4}, \frac{-5 - \sqrt{177}}{2}\right) $$
Simultaneous Equations 61A8D4
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