1.计算下列极限:-|||-(1) lim _(xarrow -1)dfrac ({x)^2+2x+1}(x-1) ;-|||-(3) lim _(xarrow 1)dfrac ({x)^2-3x+2}(x-1) =-|||-(5) lim _(xarrow 1)dfrac (sqrt {x)-1}({x)^2+5x-6} =-|||-(2) lim _(xarrow 2)dfrac (x-1)(sqrt {x+1)} ;-|||-(4) lim _(xarrow infty )dfrac ({x)^2+2x+1}({x)^4-3x+1} ;-|||-(6) lim _(harrow 0)dfrac ({(x+h))^2-(x)^2}(h) ;1.计算下列极限:-|||-(1) lim _(xarrow -1)dfrac ({x)^2+2x+1}(x-1) ;-|||-(3) lim _(xarrow 1)dfrac ({x)^2-3x+2}(x-1) =-|||-(5) lim _(xarrow 1)dfrac (sqrt {x)-1}({x)^2+5x-6} =-|||-(2) lim _(xarrow 2)dfrac (x-1)(sqrt {x+1)} ;-|||-(4) lim _(xarrow infty )dfrac ({x)^2+2x+1}({x)^4-3x+1} ;-|||-(6) lim _(harrow 0)dfrac ({(x+h))^2-(x)^2}(h) ;