7.
\((1)\)若\(\tan \alpha =3\),则\(\dfrac{\sin 2\alpha }{{{\cos }^{2}}\alpha }\)的值为____________.
\((2)\)已知直线\(y=2x+1\)与曲线\(y={{x}^{3}}+ax+b\)相切于点\((1,3)\),则实数\(b\)的值为______.
\((3)\)已知过定点\(A\)的直线\(x+my=0\)与过定点\(B\)的直线\(mx-y-m+3=0\)相交于点\(P\),则\(\left| PA \right|+\left| PB \right|\)的最大值是______________.
\((4)\)已知函数\(f(x)=1-\dfrac{m{{e}^{x}}}{{{x}^{2}}+x+1}\),若存在唯一的正整数\({{x}_{0}}\),使得\(f({{x}_{0}})\geqslant 0\),则实数\(m\)的取值范围___ 。