8.
\((1)\)已知\(-1 < \)\(a\)\( < \)\(b\)\( < 2\),则\(a\)\(-\)\(b\)的范围是__________.
\((2)\)不等式:\(|\)\(x\)\(-1|+2\)\(x\)\( > 4\)的解集是______________.
\((3)\)圆\(C\):\(ρ=-4\)\(\sin \)\(θ\)上的动点\(P\)到直线\(l\):\(ρ\)\(\sin \)\((θ+ \dfrac{π}{4} )= \sqrt{2} \)的最短距离为______.
\((4)\)参数方程\(\begin{cases}x=\cos θ \\ y=1+\cos θ\end{cases} (θ∈R)\)化为普通方程是___________.