ข้อสอบคณิต O-NET - 2559

$$\begin{gathered} \mathrm{จากโจทย์} \\ \mathrm{จะใช้วิธีกำหนดสมาชิกให้แต่ละส่วนของภาพ} \mathrm{ดังรูป} \end{gathered}$$

$$\begin{gathered} \mathrm{จะได้} A=\left\{1, 2\right\} , B=\left\{2, 3, 4\right\} , C=\left\{4\right\} \\ \upsilon =\left\{1, 2, 3, 4, 5\right\} \\ 1. \left\{1, 2\right\} \cup \left\{4\right\} = \left\{2, 3, 4\right\} \to \mathrm{ผิด} \\ 2. \left(\left\{1, 2\right\} \cap \left\{2, 3, 4\right\}\right) \cup \left\{4\right\} = \varnothing \\ \left\{2\right\} \cup \left\{4\right\} = \varnothing \to \mathrm{ผิด} \end{gathered}$$

$$\begin{gathered} 3. \left\{1, 2\right\} \cap \left\{2, 3, 4\right\} \subset \left\{2, 3, 4\right\} \cup \left\{4\right\} \\ \left\{2\right\} \subset \left\{2, 3, 4\right\} \to \mathrm{ถูก} \\ 4. \left\{1, 2\right\} - \left\{2, 3, 4\right\} \subset \left\{4\right\} \\ \left\{1\right\} \subset \left\{4\right\} \to \mathrm{ผิด} \\ 5. \left\{2, 3, 4\right\} - \left\{4\right\} \subset \left\{1, 2\right\}\text{'} \\ \left\{2, 3\right\} \subset \left\{3, 4, 5\right\} \to \mathrm{ผิด} \\ \mathrm{ดังนั้น} \mathrm{ตอบข้อ} 3 \end{gathered}$$