Rearrange Integrate
1. The problem is to express the function $y = 2 + \sqrt{x+4}$ and then rearrange it to express $x$ in terms of $y$ before integrating between the bounds $y = 3$ and $y = 6$.
2. Start with the equation:
$$y = 2 + \sqrt{x+4}$$
3. Subtract 2 from both sides:
$$y - 2 = \sqrt{x+4}$$
4. Square both sides to remove the square root:
$$(y - 2)^2 = x + 4$$
5. Rearrange to solve for $x$:
$$x = (y - 2)^2 - 4$$
6. We want to integrate $x$ with respect to $y$ from $y=3$ to $y=6$:
$$\int_{3}^{6} \big((y - 2)^2 - 4\big) \, dy$$
7. Expand $(y - 2)^2$:
$$(y - 2)^2 = y^2 - 4y + 4$$
8. Substitute back:
$$\int_{3}^{6} (y^2 - 4y + 4 - 4) \, dy = \int_{3}^{6} (y^2 - 4y) \, dy$$
9. Integrate term by term:
$$\int y^2 dy = \frac{y^3}{3}$$
$$\int (-4y) dy = -2y^2$$
10. Therefore, the integral is:
$$\left[ \frac{y^3}{3} - 2y^2 \right]_{3}^{6}$$
11. Calculate at the bounds:
At $y = 6$:
$$\frac{6^3}{3} - 2 \times 6^2 = \frac{216}{3} - 2 \times 36 = 72 - 72 = 0$$
At $y = 3$:
$$\frac{3^3}{3} - 2 \times 3^2 = \frac{27}{3} - 2 \times 9 = 9 - 18 = -9$$
12. Find the difference to get the definite integral:
$$0 - (-9) = 9$$
13. Final answer: The value of the integral is $9$.