[tex]( {2}^{40} + {2}^{39} + {2}^{38}) \div 7 = ( {2}^{38} ( {2}^{2} + 2 + 1)) \div 7 = ( {2}^{38} \times (4 + 2 + 1)) \div 7 = ( {2}^{38} \times 7) \div 7 \\ prin \: simplificare \: deducem \: ca \\ ( {2}^{38} \times 7) \div 7 = {2}^{38} [/tex]
Metoda factorului comun la puteri.
