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4*7^(n+1) +7^(n+2) ???

Răspuns :

4 *7^n *7 +7^n *7^2=

=7^n(4*7+7^2)=

= 7^n *(28+49)=

=7^n * 77=

= 7^n *7*11=

=7^(n+1) *11