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            "content": "线性方程组与高斯消元"
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            "content": "共 30 题",
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            "content": "1. 线性方程组 \\(Ax = b\\) 里，A 的每一行表示什么？A. 一个未知数B. 一条线性约束C. 一个特征值D. 学习率",
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            "content": "2. 两元一次方程组在平面上对应?\nA. 两个点\nB. 两条直线\nC. 一个圆\nD. 一条抛物线",
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            "content": "3. 两条直线相交于一点，方程组的解是？A. 无解B. 唯一解C. 无穷多解D. 两个解",
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            "content": "4. 两条直线平行但不重合，解是？  \nA. 唯一解  \nB. 无穷多解  \nC. 无解  \nD. 必有 \\(x = 0\\)",
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            "content": "5. 两条直线重合，解是？\nA. 无解\nB. 唯一解\nC. 无穷多解\nD. 只有原点",
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            "content": "6. n 个方程 n 个未知数，是否一定有唯一解？\nA. 一定\nB. 不一定，行可能成比例（奇异）",
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            "angle": 0,
            "content": "C. 一定无解  \nD. 一定无穷解",
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        },
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            "bbox": [
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            "angle": 0,
            "content": "7. 高斯消元的目标形状是?\nA. 对角且全 1\nB. 上三角（再回代）\nC. 下三角后停止\nD. 随机稀疏",
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            "content": "8. 消元允许的行操作不包括?\nA. 交换两行\nB. 一行乘非零数\nC. 一行加减另一行的倍数\nD. 把某一列任意改掉",
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            "content": "9. 回代是指？A. 从第一行往下猜B. 从上三角最后一行开始，逐个往回求未知数C. 随机抽样D. 求逆后再乘",
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            "content": "10. 主元接近 0 时，常用做法是？\nA. 直接除\nB. 换一行较大主元上来（列主元）\nC. 把方程扔掉\nD. 改用梯度下降",
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            "content": "11. 矩阵的秩，直观是？\nA. 元素个数\nB. 真正独立的约束（非零行）条数\nC. 最大元素\nD. 条件数的倒数",
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            "content": "12. 秩(A)=秩([A|b])=n（方阵满秩）意味着？\nA. 无解\nB. 唯一解",
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            "content": "C. 无穷解\nD. 一定病态",
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            "content": "13. 秩(A)<秩([A|b]) 意味着?\nA. 唯一解\nB. 无解\nC. 必有无穷解\nD. A 可逆",
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