1. **State the problem:** Solve the equation $$a^3 + a^2 = 36$$ for the variable $a$.
2. **Rewrite the equation:** We want to find $a$ such that $$a^3 + a^2 - 36 = 0$$.
3. **Factor the equation if possible:** Factor out the common term $a^2$ from the first two terms:
$$a^2(a + 1) - 36 = 0$$
4. **Isolate terms:** Rewrite as
$$a^2(a + 1) = 36$$
5. **Try possible integer roots:** Since 36 is a perfect square and cube, test integer values for $a$.
6. **Test $a=3$:**
$$3^3 + 3^2 = 27 + 9 = 36$$ which satisfies the equation.
7. **Test $a=-4$:**
$$(-4)^3 + (-4)^2 = -64 + 16 = -48
eq 36$$
8. **Check for other roots:** The equation is cubic, so there may be other roots. Use the Rational Root Theorem or numerical methods.
9. **Use substitution or numerical methods:** Since $a=3$ works, divide the cubic polynomial by $(a-3)$:
$$a^3 + a^2 - 36 = (a - 3)(a^2 + 4a + 12)$$
10. **Solve quadratic:**
$$a^2 + 4a + 12 = 0$$
Use quadratic formula:
$$a = \frac{-4 \pm \sqrt{4^2 - 4 \times 1 \times 12}}{2} = \frac{-4 \pm \sqrt{16 - 48}}{2} = \frac{-4 \pm \sqrt{-32}}{2}$$
11. **Simplify roots:**
$$a = \frac{-4 \pm 4i\sqrt{2}}{2} = -2 \pm 2i\sqrt{2}$$
12. **Final solutions:**
- Real root: $$a = 3$$
- Complex roots: $$a = -2 + 2i\sqrt{2}$$ and $$a = -2 - 2i\sqrt{2}$$
**Answer:** The real solution is $$\boxed{3}$$.
Solve Cubic 92488B
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