Đáp án:
\(\begin{array}{l}
a)\quad A = \{k\in N,\ k < 5\}\\
b)\quad B = \{4k\ \vert\ k\in\Bbb N,\ k < 5\}\\
c)\quad C = \{2^k\ \vert\ k\in\Bbb N,\ k< 5\}\\
d)\quad D = \left\{\left(-\dfrac13\right)^k\Bigg|\ k\in\Bbb N^*,\ k < 5\right\}
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
a)\\
A = \{0;1;2;3;4\}\Leftrightarrow A = \{k\in N,\ k < 5\}\\
b)\\
B = \{0;4;8;12;16\} \Leftrightarrow B = \{4k\ \vert\ k\in\Bbb N,\ k < 5\}\\
c)\\
C = \{1;2;4;8;16\} \Leftrightarrow C = \{2^k\ \vert\ k\in\Bbb N,\ k< 5\}\\
d)\\
D = \left\{-\dfrac13;\dfrac19;-\dfrac{1}{27};\dfrac{1}{81}\right\}\Leftrightarrow D = \left\{\left(-\dfrac13\right)^k\Bigg|\ k\in\Bbb N^*,\ k < 5\right\}
\end{array}\)
