Question

Answer 1

\(3,\\ A=\left\{x\in N|x< 5\right\}\\ B=\left\{x=4k|k\in N;k< 5\right\}\\ C=\left\{x=2^n|n\in N;n< 5\right\}\)

Answer 2

a: A={\(x\in N\)|x<5}

b: B={\(x\in N\)|\(\left\{{}\begin{matrix}x< 20\\x⋮4\end{matrix}\right.\)}