Question

Вычислить неопределенный интеграл ⌡(x+2)/(x^2+x+1)dx

Answer 1

$\int {\frac{x+2}{x^2+x+1}} \, dx = \frac{1}{2}\int{\frac{2x+1}{x^2+x+1}} \, dx +\frac{3}{2}\int{\frac{1}{x^2+x+1}} \, dx = \\ = \frac{1}{2}\int{\frac{1}{x^2+x+1}} \, d(x^2+x+1) +\frac{3}{2}\int{\frac{1}{x^2+2\cdot\frac{1}{2}x+\frac{1}{4}-\frac{1}{4}+1}} \, dx = \\ = \frac{1}{2}\ln|x^2+x+1| +\frac{3}{2}\int{\frac{1}{(x+\frac{1}{2})^2+\frac{3}{4}}} \, dx = \\ = \frac{1}{2}\ln|x^2+x+1| +\frac{3}{2}\int{\frac{1}{(x+\frac{1}{2})^2+(\frac{\sqrt{3}}{2})^2}} \, d(x+\frac{1}{2}) = \\$
$= \frac{1}{2}\ln|x^2+x+1| +\frac{3}{2}(\pm\frac{2}{\sqrt{3}}arctg\frac{2(x+\frac{1}{2})}{\sqrt{3}})+C= \\ = \frac{1}{2}\ln(x^2+x+1) \pm \sqrt{3}arctg\frac{2x+1}{\sqrt{3}})+C$