اگر $f(x)=\left\{ \begin{align} & \frac{x-\sqrt{x}}{1-{{x}^{2}}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x \gt 1 \\ & a[-x]+[-3x]\,\,\,\,\,\,\,\,\,x \lt 1 \\ & b+1\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x=1 \\ \end{align} \right.$ در $x=1$ پیوسته باشد، $\underset{x\to {{(-1)}^{-}}}{\mathop{\lim }}\,f(x)$ کدام است؟ ($[ ]$ نماد جزء صحیح است.)
1 )
$-\frac{3}{4}$
2 )
$-\frac{13}{4}$
3 )
$-\frac{1}{4}$
$\frac{1}{4}$