3.计算下列极限.-|||-(1) lim _(xarrow 2)(-2) ;-|||-(3) lim _(xarrow 2)dfrac ({x)^2-16}(x-4) ;-|||-(5) lim _(xarrow 1)(dfrac (1)(1-x)-dfrac (3)(1-{x)^3}) ;-|||-(7) lim _(xarrow 1)dfrac (sqrt {x+3)-2}(x-1) ;-|||-(9) lim _(xarrow infty )dfrac (9{x)^4+3(x)^2-10}(3{x)^4+(x)^3-(x)^2+1} ;-|||-(2) lim _(xarrow 1)((x)^3-(x)^2+x-1) ;-|||-(4) lim _(xarrow 3)dfrac ({x)^2-9}(x-3) ;-|||-(6) lim _(xarrow 0)dfrac ({(x+h))^3-(x)^3}(h) ;-|||-(8) lim _(xarrow +infty )sqrt (x)(sqrt (x+2)-sqrt (x+1))-|||-(10) lim _(xarrow infty )dfrac ({x)^3-2(x)^2+5}(100{x)^2+15} -