Edexcel IGCSE Maths 复习笔记 2.17.1 Inequalities on Graphs - Drawing

How do we draw inequalities on a graph?

• First, see Straight Line Graphs and Linear Inequalities

Once you do… 

1. DRAW the line (as if using “=”) for each inequalityUse a solid line for ≤ or ≥ (to indicate the line is included)

   Use dotted line for < or > (to indicate the line is not included)

2. DECIDE which side of line is wanted: 

   Below line if ≤ or <Above line if ≥ or >

   (Use the point (0, 0) as a test if unsure)

3. Shade UNWANTED side of each line (unless the question says otherwise) 

   This is because it is easier, with pen/pencil/paper at least, to see which region has not been shaded at all than it is to look for a region that has been shaded 2-3 times or more(Graphing software often shades the area that is required but this is easily overcome by reversing the inequality sign)