Question

Найти неопределенный интеграл (3x+2)/sqrt(x^2+2x+16)dx

Answer 1

$\int \frac{3x+2}{x^2+2x+16}dx=\int \frac{3x+2}{(x+1)^2+15}dx=[x+1=t,x=t-1,dx=dt]=\\\\=\int \frac{3(t-1)+2}{t^2+15}dt=\int \frac{3t-1}{t^2+15}dx=\frac{3}{2}\int \frac{2t\, dt}{t^2+15}-\frac{dt}{t^2+15}=\\\\=\frac{3}{2}ln|t^2+15|-\frac{1}{\sqrt{15}}arctg\frac{t}{\sqrt{15}}+C=\\\\\frac{3}{2}ln|x^2+2x+16|-\frac{1}{\sqrt{15}}arctg\frac{x+1}{\sqrt{15}}+C$