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Dati factor comun si apoi efectuati :
a) -[tex] \frac{5}{7} [/tex] ·[tex] \frac{1}{3} [/tex] + (-[tex] \frac{4}{21} [/tex]) · [tex] \frac{1}{3} [/tex]


Răspuns :

[tex] \frac{5}{7} \frac{1}{3} +(- \frac{4}{21}) \frac{1}{3} \\ =\frac{1}{3} ( \frac{5}{7} - \frac{4}{21} ) \\ =\frac{1}{3} ( \frac{15-4}{21} ) \\ =\frac{1}{3} ( \frac{11}{21} ) \\ = \frac{11}{63} [/tex]