📏 数轴生成器（点、区间、不等式）Number Line Generator
按起点、终点和刻度间隔画出数轴，可以标出实心点、空心点、区间（如 [−2, 3)）和不等式（如 x ≥ 1、−1 < x ≤ 4），同时给出区间记号，并下载为 SVG 图片。Draw a number line from a start, an end and a tick step, and mark closed or open points, intervals such as [−2, 3) and inequalities such as x ≥ 1 or −1 < x ≤ 4. Each mark is also given in interval notation, and the line downloads as an SVG image.
使用说明与常见问题How-to & FAQ
「数轴生成器（点、区间、不等式）」是什么？What is the Number Line Generator tool?
按起点、终点和刻度间隔画出数轴，可以标出实心点、空心点、区间（如 [−2, 3)）和不等式（如 x ≥ 1、−1 < x ≤ 4），同时给出区间记号，并下载为 SVG 图片。Draw a number line from a start, an end and a tick step, and mark closed or open points, intervals such as [−2, 3) and inequalities such as x ≥ 1 or −1 < x ≤ 4. Each mark is also given in interval notation, and the line downloads as an SVG image.
如何使用「数轴生成器（点、区间、不等式）」？How do I use the Number Line Generator tool?
在「数轴生成器（点、区间、不等式）」中，填写「起点」、「终点」、「刻度间隔」、「每隔几个刻度标数字」等参数，结果会随输入实时计算并显示在下方。In the Number Line Generator: Fill in "Start", "End", "Tick step", "Label every n ticks"; results are recalculated instantly as you type.
标记怎么写？How do I write the marks?
每行一个：数字（如 3）是实心点；前面加 o（如 o 4）是空心点；区间用方括号表示包含端点、圆括号表示不包含，如 [1, 3)、(-inf, 2]；也可以直接写不等式 x > 2、x <= -1、-1 < x <= 4（≤ ≥ 也可以）。每个标记会同时显示对应的区间记号。One per line: a number (3) is a closed point; put o in front (o 4) for an open point. Intervals use square brackets for included ends and round brackets for excluded ones: [1, 3), (-inf, 2]. You can also type inequalities such as x > 2, x <= -1 or -1 < x <= 4 (≤ and ≥ work too). Each mark is also shown in interval notation.
实心点和空心点分别代表什么？What do closed and open dots mean?
实心点表示包含这个端点（≤、≥ 或方括号），空心点表示不包含（<、> 或圆括号）。延伸到无穷的区间在数轴末端画箭头。A closed dot means the end is included (≤, ≥ or a square bracket); an open dot means it is excluded (<, > or a round bracket). Intervals running to infinity end in an arrow at the end of the line.
刻度和数字的数量有限制吗？Is there a limit on ticks?
刻度数（终点 − 起点）÷ 刻度间隔须在 1–200 之间，以免图太密看不清；刻度多时可以设置“每隔几个刻度标数字”，例如每 5 格标一次。The number of ticks, (end − start) ÷ step, must be from 1 to 200 so the line stays readable; with many ticks use 'Label every n ticks', e.g. every 5.
能保存图片吗？Can I save the picture?
可以，点“下载 SVG”保存矢量图，放进 Word、PPT 或网页都不会模糊，也可以用浏览器打开后另存为 PNG。Yes — 'Download SVG' saves a vector image that stays sharp in Word, PowerPoint or a web page; open it in a browser to save a PNG if you need one.
计算精度如何？How precise are the results?
「数轴生成器（点、区间、不等式）」使用 JavaScript 双精度浮点数（约 15–16 位有效数字）；极大或极小的数值可能存在精度误差。The Number Line Generator uses double-precision floating point (about 15–16 significant digits); very large or very small values may lose precision.
「数轴生成器（点、区间、不等式）」免费吗？需要注册吗？Is the Number Line Generator free? Do I need an account?
「数轴生成器（点、区间、不等式）」完全免费，无需注册或安装，打开网页即可使用，手机和电脑都能用；输入的内容只在你的浏览器本地处理。The Number Line Generator is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.