$x_1=\frac{\sqrt{3}}{2},x_2=-\frac{\sqrt{3}}{2}$
$\frac{-5 + \sqrt{17}}{4}$
$\frac{-5 - \sqrt{17}}{4}$
$\frac{-\sqrt{5}\pm\sqrt{11}}{2}$
$\frac{-\sqrt{5}+\sqrt{11}}{2}$
$\frac{-\sqrt{5}-\sqrt{11}}{2}$
$解:a=1,b=-2\sqrt {3},c=-1$ $△=12+4=16$ $x=\frac {2\sqrt {3}±\sqrt {16}}{2}$ $x_{1}=2+\sqrt {3},x_{2}=-2+\sqrt {3}$ $解:a=2,b=1,c=-2$ $△=1+16=\sqrt {17}$ $x=\frac {-1±\sqrt {17}}{4}$ $x_{1}=\frac {-1+\sqrt {17}}{4},x_{2}=\frac {-1-\sqrt {17}}{4}$ $解:a=1,b=-2\sqrt {5},c=-4$ $△=20+16=36$ $x=\frac {2\sqrt {5}±\sqrt {36}}{2}$ $x_{1}=3+\sqrt {5},x_{2}=-3+\sqrt {5}$ $解:4x^{2}+2x-1=0$ $a=4,b=2,c=-1$ $△=4+16=20$ $x=\frac {-2±\sqrt {20}}{8}$ $x_{1}=\frac {-1+\sqrt {5}}{4},x_{2}=\frac {-1-\sqrt {5}}{4}$
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