1. **State the problem:** We need to evaluate the integral $$\int \frac{1}{\sqrt{2x^{2}+3x+2}}\,dx$$.
2. **Identify the quadratic expression:** The expression inside the square root is $$2x^{2}+3x+2$$.
3. **Complete the square:** To simplify the integral, we complete the square for the quadratic.
$$2x^{2}+3x+2 = 2\left(x^{2}+\frac{3}{2}x\right)+2$$
Inside the parentheses, complete the square:
$$x^{2}+\frac{3}{2}x = \left(x+\frac{3}{4}\right)^{2} - \left(\frac{3}{4}\right)^{2} = \left(x+\frac{3}{4}\right)^{2} - \frac{9}{16}$$
So,
$$2x^{2}+3x+2 = 2\left[\left(x+\frac{3}{4}\right)^{2} - \frac{9}{16}\right] + 2 = 2\left(x+\frac{3}{4}\right)^{2} - \frac{18}{16} + 2 = 2\left(x+\frac{3}{4}\right)^{2} - \frac{9}{8} + 2$$
Simplify constants:
$$-\frac{9}{8} + 2 = -\frac{9}{8} + \frac{16}{8} = \frac{7}{8}$$
Therefore,
$$2x^{2}+3x+2 = 2\left(x+\frac{3}{4}\right)^{2} + \frac{7}{8}$$
4. **Rewrite the integral:**
$$\int \frac{1}{\sqrt{2\left(x+\frac{3}{4}\right)^{2} + \frac{7}{8}}} \, dx$$
5. **Substitute:** Let
$$u = x + \frac{3}{4} \implies du = dx$$
The integral becomes:
$$\int \frac{1}{\sqrt{2u^{2} + \frac{7}{8}}} \, du$$
6. **Factor constants inside the square root:**
$$\sqrt{2u^{2} + \frac{7}{8}} = \sqrt{2\left(u^{2} + \frac{7}{16}\right)} = \sqrt{2} \sqrt{u^{2} + \frac{7}{16}}$$
So the integral is:
$$\int \frac{1}{\sqrt{2} \sqrt{u^{2} + \frac{7}{16}}} \, du = \frac{1}{\sqrt{2}} \int \frac{1}{\sqrt{u^{2} + \left(\frac{\sqrt{7}}{4}\right)^{2}}} \, du$$
7. **Use the standard integral formula:**
$$\int \frac{1}{\sqrt{u^{2} + a^{2}}} \, du = \ln\left| u + \sqrt{u^{2} + a^{2}} \right| + C$$
Here, $$a = \frac{\sqrt{7}}{4}$$.
8. **Apply the formula:**
$$\frac{1}{\sqrt{2}} \ln\left| u + \sqrt{u^{2} + \left(\frac{\sqrt{7}}{4}\right)^{2}} \right| + C$$
9. **Substitute back for $$u$$:**
$$\frac{1}{\sqrt{2}} \ln\left| x + \frac{3}{4} + \sqrt{\left(x + \frac{3}{4}\right)^{2} + \frac{7}{16}} \right| + C$$
**Final answer:**
$$\boxed{\int \frac{1}{\sqrt{2x^{2}+3x+2}}\,dx = \frac{1}{\sqrt{2}} \ln\left| x + \frac{3}{4} + \sqrt{\left(x + \frac{3}{4}\right)^{2} + \frac{7}{16}} \right| + C}$$
Integral Quadratic D085F0
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