()-|||-(2) (int )_(-infty )^+infty dfrac (2x)(1+{x)^2}dx=lim _(aarrow +infty )(int )_(-a)^adfrac (2x)(1+{x)^2}dx=0. ()-|||-(3) (int )_(0)^4dfrac (dx)({(x-3))^2}=-dfrac (1)(x-3)(|)^4=-dfrac (4)(3) ()

(int )_(e)^+infty dfrac (dx)(x{ln )^2x}= __

(int )_(-infty )^+infty (x)^2(e)^-a(x^2)dx=dfrac (1)(2)sqrt (dfrac {pi )({a)^3}}

(int )_(-infty )^+infty dfrac (dx)({x)^2+2x+2}..

(2) (int )_(-infty )^+infty dfrac (dx)({x)^2+2x+2}

lim _(xarrow infty )((1-dfrac {1)(2x))}^x+2= ).A.lim _(xarrow infty )((1-dfrac {

(单选题)lim _(xarrow infty )((dfrac {x-4)(x))}^2x=____lim _(xarrow infty )((dfrac {

(int )_(0)^+infty dfrac (x{e)^-x}({(1+{e)^-x)}^2}dx= ()-|||-__

lim _(xarrow infty )xsin dfrac (2x)({x)^2+1}=________.________.

.lim _(xarrow infty )xsin dfrac (1)(2x)= __

(4) (int )_(0)^+infty dfrac (dx)((1+x)(1+{x)^2)}