1 7 49 343 (?)

49 : 343 :: 64 : ?

Simplify (b ^(2) - 49) (b+7) + 343

Solve for x : (49)^(x + 4) = 7^(2) xx (343)^(x + 1)

Find the sum to infinity of the series . (i) 1+ (2)/(11) + (3)/(121) + (4)/(1331) + … + n((1)/(11))^(n-1) + … (ii) 1 + (4)/(7) + (9)/(49) + (16) / (343) +…+ n^(2) ((1)/(7))^(n-1) +…