1.计算下列极限:-|||-(1) lim _(xarrow 2)dfrac ({x)^2+5}(x-3) .-|||-(3) lim _(xarrow 1)dfrac ({x)^2-2x+1}({x)^2-1}-|||-(5) lim _(harrow 0)dfrac ({(x+h))^2-(x)^2}(h) :-|||-(7) lim _(xarrow infty )dfrac ({x)^2-1}(2{x)^2-x-1} ;-|||-(9) lim _(xarrow a)dfrac ({x)^2-6x+8}({x)^2-5x+4} =-|||-(11) lim _(narrow infty )(1+dfrac (1)(2)+dfrac (1)(4)+... +dfrac (1)({2)^n})-|||-1/2^n);(12)-|||-(13) lim _(narrow infty )dfrac ((n+1)(n+2)(n+3))(5{n)^2} ;-|||-(2) lim _(xarrow sqrt {3)}dfrac ({x)^2-3}({x)^2+1} ;-|||-(4) lim _(xarrow 0)dfrac (4{x)^3-2(x)^2+x}(3{x)^2+2x} =-|||-(6) lim _(xarrow infty )(2-dfrac (1)(x)+dfrac (1)({x)^2}) ;-|||-(8) lim _(xarrow infty )dfrac ({x)^2+x}({x)^4-3(x)^2+1} ;-|||-(10) lim _(xarrow infty )(1+dfrac (1)(x))(2-dfrac (1)({x)^2}) ;-|||-lim _(narrow infty )dfrac (1+2+3+... +(n-1))({1)^2} ;-|||-(14) lim _(xarrow 1)(dfrac (1)(1-x)-dfrac (3)(1-{x)^3}) -