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解：??$2x^2-3x - 3 = 0$??
??$x^2-\frac {3}{2}x=\frac {3}{2}$??
??$x^2-\frac {3}{2}x+\frac {9}{16}=\frac {3}{2}+\frac {9}{16}$??
??$(x-\frac {3}{4})^2=\frac {33}{16}$??
??$x-\frac {3}{4}=±\frac {\sqrt {33}}4$??
??$x_{1}=\frac {3 + \sqrt {33}}{4}，$????$x_{2}=\frac {3 - \sqrt {33}}{4}$??
解：??$4x^2-x - 1 = 0$??
??$x^2-\frac {1}{4}x=\frac {1}{4}$??
??$x^2-\frac {1}{4}x+\frac {1}{64}=\frac {1}{4}+\frac {1}{64}$??
??$(x-\frac {1}{8})^2=\frac {17}{64}$??
??$x-\frac {1}{8}=±\frac {\sqrt {17}}8$??
??$x_{1}=\frac {1 + \sqrt {17}}{8}，$????$x_{2}=\frac {1 - \sqrt {17}}{8}$??
解：??$2y^2+5y + 1 = 0$??
??$y^2+\frac {5}{2}y=-\frac {1}{2}$??
??$y^2+\frac {5}{2}y+\frac {25}{16}=-\frac {1}{2}+\frac {25}{16}$??
??$(y+\frac {5}{4})^2=\frac {17}{16}$??
??$y+\frac {5}{4}=±\frac {\sqrt {17}}{4}$??
??$y_{1}=\frac {-5 + \sqrt {17}}{4}，$????$y_{2}=\frac {-5 - \sqrt {17}}{4}$??
解：??$3x^2+5 = 9x$??
??$x^2-3x=-\frac {5}{3}$??
??$x^2-3x+\frac {9}{4}=-\frac {5}{3}+\frac {9}{4}$??
??$(x-\frac {3}{2})^2=\frac {7}{12}$??
??$x-\frac {3}{2}=±\frac {\sqrt {21}}6$??
??$x_{1}=\frac {9 + \sqrt {21}}{6}，$????$x_{2}=\frac {9 - \sqrt {21}}{6}$??
解：??$x^2-3x + 2 = 0$??
??$a=1，$????$b=-3，$????$c=2$??
??$b^2-4ac=(-3)^2-4×1×2$??
??$=1＞0$??
??$x=\frac {3±\sqrt 1}{2×1}$??
??$x_{1}=1，$????$x_{2}=2$??
解：??$2x^2+x - 1 = 0$??
??$a=2，$????$b=1，$????$c=-1$??
??$b^2-4ac=1^2-4×2×(-1)$??
??$=9＞0$??
??$x=\frac {-1±\sqrt 9}{2×2}$??
??$x_{1}=\frac {1}{2}，$????$x_{2}=-1$??
解：??$x^2-2x - 3 = 0$??
??$a=1，$????$b=-2，$????$c=-3$??
??$b^2-4ac=(-2)^2-4×1×(-3)$??
??$=16＞0$??
??$x=\frac {2±\sqrt {16}}{2×1}$??
??$x_{1}=3，$????$x_{2}=-1$??
解：??$y^2+3y - 4 = 0$??
??$a=1，$????$b=3，$????$c=-4$??
??$b^2-4ac=3^2-4×1×(-4)$??
??$=25＞0$??
??$y=\frac {-3±\sqrt {25}}{2×1}$??
??$y_{1}=-4，$????$y_{2}=1$??
解：??$x^2+9x + 20 = 0$??
??$a=1，$????$b=9，$????$c=20$??
??$b^2-4ac=9^2-4×1×20$??
??$=1＞0$??
??$x=\frac {-9±\sqrt 1}{2×1}$??
??$x_{1}=-4，$????$x_{2}=-5$??
解：??$x^2+10x + 25 = 0$??
??$a=1，$????$b=10，$????$c=25$??
??$b^2-4ac=10^2-4×1×25$??
??$=0$??
??$x=\frac {-10±\sqrt 0}{2×1}$??
??$x_{1}=x_{2}=-5$??
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