中文辅助说明
学习模式会显示直线、抛物线等边界及对应不等式，帮助你理解实线与虚线、边界上方与下方的意义。之后可以练习点击正确区域，或根据已涂色的图像反写不等式，在“看式子涂区域”和“看区域写式子”之间双向训练。
Interactive sandbox
Move a boundary, then watch the intersection change
Drag either sloping line or the vertical line. Change a sign below to see how every condition contributes to the final region.
Drag a boundary directly on the graph. The blue shading is the intersection of all conditions.