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   "source": [
    "Consider the following piece of code:\n",
    "\n",
    "```python\n",
    "def f(x):\n",
    "    if x == 0 or x == 1:\n",
    "        return x\n",
    "    return f(x - 1) + f(x - 2)\n",
    "```"
   ]
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  {
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   "source": [
    "---\n",
    "## Part A (1 point)\n",
    "\n",
    "Describe, in words, what this code does, and how it does it."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "nbgrader": {
     "grade": true,
     "grade_id": "part-a",
     "points": "1",
     "solution": true
    }
   },
   "source": [
    "This function computes the fibonnaci sequence using recursion. The base cases are $x=0$ and $x=1$, in which case the function will return 0 or 1, respectively. In all other cases, the function will call itself to find the $x-1$ and $x-2$ fibonnaci numbers, and then add them together."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
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    }
   },
   "source": [
    "---\n",
    "## Part B (2 points)\n",
    "\n",
    "For what inputs will this function not behave as expected? What will happen?"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "nbgrader": {
     "grade": true,
     "grade_id": "part-b",
     "points": 2,
     "solution": true
    }
   },
   "source": [
    "The function will not work correctly for inputs less than zero. Such inputs will result in an infinite recursion, as the function will keep subtracting one but never reach a base case that stops it."
   ]
  }
 ],
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