8.[单选题]-|||-int dfrac (3{x)^4+3(x)^2+1}({x)^2+1}dx= () .-|||-A) ^2+arctan x+C:-|||-B ^3+tan x+C:-|||-C ^3+arctan x+C:-|||-D ^3+arctan x+C.

int dfrac (2{x)^3+2x+3}({x)^2+1}dx=(x)^a+b(x)+C 则 cdot b(x)=

int (x)^3(e)^-(x^2)dx=(,,,,,)A、dfrac(1)(2)(e)^-(x^2)((x)^2+1)+CB、-dfrac(1)(2)(e)

(43) int dfrac ({x)^3+1}({({x)^2+1)}^2}dx ;

(44) int dfrac ({x)^3+1}({({x)^2+1)}^2}dx,

(44) int dfrac ({x)^3+1}({({x)^2+1)}^2}dx.

(44) int dfrac ({x)^3+1}({({x)^2+1)}^2}dx.

int dfrac ({x)^2}({x)^2+1}dx ,

3.int dfrac (dx)(sqrt {{({x)^2+1)}^3}}=3.

9、 int dfrac (1)(({x)^2+1)(x)^2}dx= __ 。

int dfrac ({x)^2+1}({(x+1))^2(x-1)}dx；；