1.按定义证明下列极限:-|||-(1) lim _(xarrow -infty )dfrac (6x+5)(x)=6;-|||-(2) lim _(xarrow 2)((x)^2-6x+10)=2;-|||-(4) lim _(xarrow {2)^-}sqrt (4-{x)^2}=0;-|||-(5) lim _(xarrow {x)_(0)}cos x=cos (x)_(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. Mllim l ar... I. I . i-|||-(3) lim _(xarrow infty )dfrac ({x)^2-5}({x)^2-1}=1;