Question

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$7^{11+12+13+...+30}$=($7^{n}$)³·49

Answer 1

[tex]11+12+13+...+30= \frac{30*31-10*11}{2}=410 \\ 7^{410} = 7^{3n+2} \\ 410=3n+2 \\ 3n=408 \\ n=136[/tex]