Question

F(x)=-2x^3+1/3x^2-1 найтм общий вид первообразной

Answer 1

$f(x)= \frac{-2x^3+1}{3x^2-1}=-\frac{2}{3}x+\frac{-\frac{2}{3}x+1}{3x^2-1}=-\frac{2}{3}x- \frac{2}{3}\cdot \frac{x}{3x^2-1}+\frac{1}{3x^2-1}\; ;\\\\F(x)=-\frac{2}{3}\cdot \int x\, dx-\frac{2}{3}\cdot \int \frac{x\, dx}{3x^2-1}+\int \frac{dx}{3x^2-1}=\\\\=-\frac{2}{3}\cdot \frac{x^2}{2}-\frac{2}{3\cdot 6}\cdot \int \frac{6x\, dx}{3x^2-1}+ \frac{1}{\sqrt3}\cdot \int \frac{\sqrt3\, dx}{(\sqrt3x)^2-1^2}=\\\\=-\frac{x^2}{3}-\frac{1}{9}\cdot \int \frac{d(3x^2-1)}{3x^2-1}+\frac{1}{\sqrt3}\cdot \int \frac{d(\sqrt3x)}{(\sqrt3x)^2-1}=\\\\=-\frac{x^2}{3}-\frac{1}{9}\cdot ln|3x^2-1|+\frac{1}{\sqrt3}\cdot \frac{1}{2}\cdot ln| \frac{\sqrt3x-1}{\sqrt3x+1}|+C$