1. **State the problem:** Solve the equation $y^2 + y^3 = 12$ for $y$.
2. **Rewrite the equation:** The equation can be written as
$$y^3 + y^2 = 12$$
3. **Factor the left side:** Factor out the common term $y^2$:
$$y^2(y + 1) = 12$$
4. **Isolate terms:** We want to find values of $y$ such that this holds true.
5. **Try possible rational roots:** Since the equation is cubic, try simple integer values like $y=1, 2, 3$:
- For $y=1$: $1^3 + 1^2 = 1 + 1 = 2 \neq 12$
- For $y=2$: $2^3 + 2^2 = 8 + 4 = 12$ which satisfies the equation.
6. **Check for other roots:** Divide the cubic polynomial $y^3 + y^2 - 12 = 0$ by $(y-2)$:
$$\frac{y^3 + y^2 - 12}{y - 2} = y^2 + 3y + 6$$
7. **Solve the quadratic:** Set
$$y^2 + 3y + 6 = 0$$
Use the quadratic formula:
$$y = \frac{-3 \pm \sqrt{3^2 - 4 \times 1 \times 6}}{2 \times 1} = \frac{-3 \pm \sqrt{9 - 24}}{2} = \frac{-3 \pm \sqrt{-15}}{2}$$
8. **Interpret roots:** The discriminant is negative, so the quadratic has no real roots.
9. **Final answer:** The only real solution is
$$y = 2$$
Solve Cubic 1794Da
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