ข้อสอบคณิต O-NET - 2556

$$\begin{gathered} \mathrm{จากโจทย์} \\ \mathrm{กำหนดสมาชิกในแต่ละส่วนดังนี้} \end{gathered}$$

$$\begin{gathered} \mathrm{จะได้} U = \left\{1, 2, 3, 4, 5, 6\right\} \\ A = \left\{2, 3\right\} \\ B = \left\{1, 2, 3, 4\right\} \\ C = \left\{3, 4, 5\right\} \end{gathered}$$

$$\begin{gathered} \mathrm{จะได้} \left(B-A\right)\text{'}\cap C \\ = \left(\left\{1, 2, 3, 4\right\}-\left\{2, 3\right\}\right)\text{'}\cap \left\{3, 4, 5\right\} \\ = \left(\left\{1, 4\right\}\right)\text{'}\cap \left\{3, 4, 5\right\} \\ = \left\{2, 3, 5, 6\right\}\cap \left\{3, 4, 5\right\} \\ = \left\{3, 5\right\} \\ \mathrm{ดังนั้น} \mathrm{ตอบข้อ} 1 \end{gathered}$$