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Calculati:(4-n)*(5-n)=12

Răspuns :

pai n=1 
Verificare:   (4-1)x(5-1)=12
                    3 x 4=12
20-4n-5n-n²=12
n²-9n+18=0
Δ=(-9)²-4*18=9
n1=(9-3)/2=3
n2=(9+3)/2=6
n={3, 6}