Ellipse Equation
1. We are given the equation of a conic: $$16x^2 + 25y^2 + 160x + 200y + 400 = 0$$.
2. First, group the $x$ and $y$ terms:
$$16x^2 + 160x + 25y^2 + 200y + 400 = 0$$.
3. Factor coefficients of squared terms:
$$16(x^2 + 10x) + 25(y^2 + 8y) + 400 = 0$$.
4. Complete the square for $x$:
Take half of 10, which is 5, square it: $5^2 = 25$.
Add and subtract $16 \times 25 = 400$ inside the expression:
$$16(x^2 + 10x + 25 - 25) + 25(y^2 + 8y) + 400 = 0$$
$$16((x + 5)^2 - 25) + 25(y^2 + 8y) + 400 = 0$$.
5. Complete the square for $y$:
Half of 8 is 4, square it: $4^2 = 16$.
Add and subtract $25 \times 16 = 400$:
$$16((x + 5)^2 - 25) + 25((y + 4)^2 - 16) + 400 = 0$$.
6. Expand and simplify:
$$16(x + 5)^2 - 400 + 25(y + 4)^2 - 400 + 400 = 0$$
$$16(x + 5)^2 + 25(y + 4)^2 - 400 = 0$$.
7. Add 400 to both sides:
$$16(x + 5)^2 + 25(y + 4)^2 = 400$$.
8. Divide both sides by 400:
$$\frac{16(x + 5)^2}{400} + \frac{25(y + 4)^2}{400} = 1$$
which simplifies to
$$\frac{(x + 5)^2}{25} + \frac{(y + 4)^2}{16} = 1$$.
This is the equation of an ellipse centered at $(-5, -4)$ with semi-major axis 5 and semi-minor axis 4.
**Final answer:**
$$\frac{(x + 5)^2}{25} + \frac{(y + 4)^2}{16} = 1$$