$\text{a)}A=\left\{1,2,4,5,10,20\right\}$  

$\text{b)}B=\left\{-4,-5,0,1,-3,7\right\}$  

$\text{c)}C=\left\{-2\sqrt{5},-\sqrt{5},0,17\sqrt{5},100\sqrt{5}\right\}$  

$\text{d)}D=\left\{0,1,4,9,16,25,36,49,64,81\right\}$  

Całkowite liczby jednocyfrowe to -9, -8, -7, ..., -1, 0, 1, ..., 7, 8, 9. Ponadto, (-9)²=9²=81.

$\text{e)}E=\left\{4,2,\frac{4}{3},1,\frac{4}{5},\frac{2}{3},\frac{4}{7},\frac{1}{2},\frac{4}{9},\frac{2}{5},\frac{4}{11},\dots ,\frac{4}{99},\frac{1}{25}\right\}$  

$\text{f)}F=\left\{1,-9,-81,-729,\dots \right\}$