Răspuns :
1) B = {x∈ℕ| x∈M₇ , 14<x<45}
M₇ < 45, dar > 14 : 21,28,35,42.
⇒ B = { 21, 28, 28, 35, 42 }
2) a) M₂₀ : 120, 140,160......
b) M₂₅ : 225, 250,275,300.
4) 72= 2³ · 3² => 12 divizori. [(3+1)*(2+1)]
225 = 5² * 3² => 9 divizori [ (2+1)*(2+1)]
300 = 2²*3*5² => 18 divizori. [(2+1)*(1+1)*(2+1)]
M₇ < 45, dar > 14 : 21,28,35,42.
⇒ B = { 21, 28, 28, 35, 42 }
2) a) M₂₀ : 120, 140,160......
b) M₂₅ : 225, 250,275,300.
4) 72= 2³ · 3² => 12 divizori. [(3+1)*(2+1)]
225 = 5² * 3² => 9 divizori [ (2+1)*(2+1)]
300 = 2²*3*5² => 18 divizori. [(2+1)*(1+1)*(2+1)]
[tex]1)x=\{21,28,35,42 \} \\ \\ 2. \ a)M_{20}= \{120,140,160,180,200,220 \} \\ \\ b) M_{25}= \{225,250,275,300 \} \\ \\ 3)D_{72}= \{1,2,3,4,6,8,9,12,18,24,36,72 \} => nr. \ divizorilor \ nr. 72 \ este \ 12 \\ \\ D_{225}= \{1,3,5,9,15,25,45,75,225 \} => nr. \ divizorilor \ nr.225 \ este \ 9 \\ \\ D_{300}= \{1,2,3,4,5,6,10,1215,20,25,30,50,60,75,100,150,300 \} \\ => nr. \ divizorilor \ nr.300 \ este \ 18[/tex]