利用泰勒公式求下列极限:-|||-(1) lim _(xarrow +infty )(sqrt [3]({x)^3+3(x)^2}-sqrt [4]({x)^4-2(x)^3});-|||-(2) lim _(xarrow 0)dfrac (cos x-{e)^-dfrac ({x^2)(2)}({x)^2[ x+ln (1-x)] }-|||-(3) lim _(xarrow 0)dfrac (1+dfrac {1)(2)(x)^2-sqrt (1+{x)^2}}((cos x-{e)^(x^2))sin (x)^2}-|||-(4) lim _(xarrow infty )[ x-(x)^2ln (1+dfrac (1)(x))] .