9.
在二次函数\(y=ax^{2}+bx+c(a\neq 0,a,b,c\)是常数\()\)中,函数\(y\)与自变量\(x\)的对应值如下表:
\(x\) | \(…\) | \(-1\) | \(-\dfrac{1}{2}\) | \(0\) | \(\dfrac{1}{2}\) | \(1\) | \(\dfrac{3}{2}\) | \(2\) | \(\dfrac{5}{2}\) | \(3\) | \(…\) |
\(y\) | \(…\) | \(-2\) | \(-\dfrac{1}{4}\) | \(1\) | \(\dfrac{7}{4}\) | \(2\) | \(\dfrac{7}{4}\) | \(1\) | \(-\dfrac{1}{4}\) | \(-2\) | \(…\) |
\((1)\)判断二次函数图象的开口方向,并写出它的顶点坐标;
\((2)\)一元二次方程\(ax^{2}+bx+c=0(a\neq 0,a,b,c\)是常数\()\)的两个根\(x_{1}\),\(x_{2}\)的取值范围是下列选项中的________.
\(①-\dfrac{1}{2} < {{x}_{1}} < 0\),\(\dfrac{3}{2} < {{x}_{2}} < 2\);
\(②-1 < {{x}_{1}} < -\dfrac{1}{2}\),\(2 < {{x}_{2}} < \dfrac{5}{2}\);
\(③-\dfrac{1}{2} < {{x}_{1}} < 0\),\(2 < {{x}_{2}} < \dfrac{5}{2}\);
\(④-1 < {{x}_{1}} < -\dfrac{1}{2}\),\(\dfrac{3}{2} < {{x}_{2}} < 2\);