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    "## 一元二次方程\n",
    "求根：用math.sqrt(x)可以求x的根\n",
    "$$\n",
    "x = \\dfrac{-b \\pm \\sqrt{b^2 - 4ac}}{2a}\n",
    "$$\n",
    "代码如下："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 44,
   "metadata": {},
   "outputs": [],
   "source": [
    "import math\n",
    "def qiugen(a,b,c):\n",
    "    dc = b/-2*a #对称轴\n",
    "    print (\"对称轴\"+str(dc))\n",
    "\n",
    "    try: #尝试求根，因为负数没法求根\n",
    "        x1 = -b+math.sqrt(b**2-4*a*c)/2*a\n",
    "        x2 = -b-math.sqrt(b**2-4*a*c)/2*a\n",
    "        if x1 == x2:\n",
    "            return \"只有一个解\",x1\n",
    "        else:\n",
    "            return \"两个解\",x1,x2\n",
    "        \n",
    "    except: \n",
    "        return \"没有根\"\n",
    "          "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 45,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "对称轴-1.0\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "('只有一个解', -2.0)"
      ]
     },
     "execution_count": 45,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "qiugen(1,2,1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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