a) x= 0,1,2, ,9
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3x = 30,31,32,33,34,35,36,37,38,39
Eliminam numerele pare: => 31,33,35,37,39
Eliminam multiplii de 3 (pt ca 30=3*2*5) => 31,35,37
Eliminam multiplii de 5 => 31,37
=> 31 / 30 si 37 / 30
Similar la b)
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1x = 10, 11, 12,13,14, 15, 16, 17, 18, 19
12= 2²*3
Eliminam numerele pare => 11,13,15,17,19
Eliminam multiplii de 3 => 11,13,17,19
