4.
已知函数\(f(x)= \dfrac {(x+a)\cdot e^{x}}{x+1}(e\)为自然对数的底数\()\),曲线\(y=f(x)\)在\((1,f(1))\)处的切线与直线\(4x+3ey+1=0\)互相垂直.
\((\)Ⅰ\()\)求实数\(a\)的值;
\((\)Ⅱ\()\)若对任意\(x∈( \dfrac {2}{3},+∞)\),\((x+1)f(x)\geqslant m(2x-1)\)恒成立,求实数\(m\)的取值范围;
\((\)Ⅲ\()\)设\(g(x)= \dfrac {(x+1)f(x)}{x( \sqrt {e}+e^{x})}\),\(T_{n}=1+2[g( \dfrac {1}{n})+g( \dfrac {2}{n})+g( \dfrac {3}{n})+…+g( \dfrac {n-1}{n})](n=2,3…).\)问:是否存在正常数\(M\),对任意给定的正整数\(n(n\geqslant 2)\),都有\( \dfrac {1}{T_{3}}+ \dfrac {1}{T_{6}}+ \dfrac {1}{T_{9}}+…+ \dfrac {1}{T_{3n}} < M\)成立?若存在,求\(M\)的最小值;若不存在,请说明理由.