Question

Решить интеграл (4x-1)/(x^(2)-8x+25)

Answer 1

$\int \frac{4x-1}{x^2-8x+25}dx=\int \frac{4x-1}{(x-4)^2+9}dx=[\, t=x-4,\; x=t+4,\; dx=dt\, ]=\\\\=\int \frac{4t+15}{t^2+9}dt=2\int \frac{2t\, dt}{t^2+9}+15\int \frac{dt}{x^2+9}=[\, 2t\, dt=d(t^2+9)\, ]=\\\\=2\, ln|t^2+9|+15\cdot \frac{1}{3}\cdot arctg\frac{t}{3}+C=\\\\=2\cdot ln|x^2-8x+25|+15\cdot arctg \frac{x-4}{3}+C$