ข้อสอบคณิต 2 - มีนาคม 2562

$$\begin{gathered} \mathrm{พิจารณาแต่ละข้อความ} \\ ก) -2+\left|-5\right| = -2+5 = 3 \to \mathrm{ถูก} \\ ข) \left.\begin{array}{r}{\left|-5\right|}^3 = {\left(5\right)}^3 = 125\\ {\left(5\sqrt{5}\right)}^2 = \left(25\right)\left(5\right)= 125\end{array}\right\} \mathrm{เท่ากัน} \to \mathrm{ถูก} \end{gathered}$$

$$\begin{gathered} ค) \sqrt[3]{3\sqrt{3}} = {\left(3^1·3^{\frac{1}{2}}\right)}^{\frac{1}{3}} \\ = {\left(3^{\frac{3}{2}}\right)}^{\frac{1}{3}} = 3^{\frac{1}{2}} = \sqrt{3} \to \mathrm{ถูก} \end{gathered}$$

$$\begin{gathered} ง) {\left({81}^{\frac{1}{3}}-{24}^{\frac{1}{3}}\right)}^3 = {\left(\sqrt[3]{81}-\sqrt[3]{24}\right)}^3 \\ = {\left(\sqrt[3]{3}-2\sqrt[3]{3}\right)}^3 \\ = {\left(\sqrt[3]{3}\right)}^3 = 3 \to \mathrm{ถูก} \\ \mathrm{ตอบ} 5 \end{gathered}$$