1.按定义证明下列极限:-|||-① lim _(xarrow infty )dfrac (6x+5)(x)=6;-|||-lim _(xarrow 2)((x)^2-6x+10)=2;-|||-(3) lim _(xarrow infty )dfrac ({x)^2-5}({x)^2-1}=1;-|||-(4) lim _(xarrow {2)^-}sqrt (4-{x)^2}=0;-|||-(5) lim _(xarrow x)cos x=cos (x)_(0)-|||-0-|||-2.根据定义2叙述 lim _(xarrow {x)_(0)}f(x)neq A.-|||-3.设 lim _(xarrow {x)_(0)}f(x)=A, 证明 lim _(harrow 0)f((x)_(0)+h)=A.-|||-4.证明:若 lim f(x)=A 则lim 1 (m