Explicație pas cu pas:
x < 30 => 5n + 7 < 30
[tex]5n < 23 \implies n < \frac{23}{5} = 4 \frac{3}{5} \\ \implies 0 \leqslant n \leqslant 4 [/tex]
n = 0 => x = 7
n = 1 => x = 12
n = 2 => x = 17
n = 3 => x = 22
n = 4 => x = 27
=> C = {7; 12; 17; 22; 27}
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30 < y < 100 <=> 30 < n² < 100
[tex] \sqrt{30} < n < \sqrt{100} \iff \sqrt{30} < n < 10 \\ 5 = \sqrt{25} < \sqrt{30} < \sqrt{36} = 6 \\ \implies 6 \leqslant n \leqslant 9[/tex]
n = 6 => y = 36
n = 7 => y = 49
n = 8 => y = 64
n = 9 => y = 81
=> D = {36; 49; 64; 81}
