Will the sum of the sequence of 1 + 2 1 + 3 1 + 4 1 + ⋯ converge or diverge?
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Simple standard approach.
The Harmonic series, as this series are called, diverges . While Margaret provided simple proof, I will use the integral. For 1 + 2 1 + 3 1 + 4 1 + ⋯ This is equal to the area of rectangle of the size 1 × n 1 . The area below the graph y = x 1 from x = 1 to n is defined by ∫ 1 n x d x = l n ( n ) < 1 + 2 1 + 3 1 + 4 1 + ⋯ + n 1 Here, as n reaches infinity, the value of l n ( n ) will reach its infinity as well, which, in turn, cause the series to diverge.
This is great and thank you very much!
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Though the numerical value of this sequence tends to grow slowly, it actually diverges to infinity.
To prove this, first consider the sequence S1= 1 + 2 1 + 4 1 + 4 1 + 8 1 + 8 1 + 8 1 + 8 1 . . . . Now rewrite it as S1 = 1 + 2 1 + 2 1 + 2 1 . . . and apparently this sequence will diverge.
The last step is to compare S1 to our original sequence: Original sequence = 1 + 2 1 + 3 1 + 4 1 + 5 1 + 6 1 + 7 1 + 8 1 . . . S1= 1 + 2 1 + 4 1 + 4 1 + 8 1 + 8 1 + 8 1 + 8 1 . . .
Obviously, the original sequence appears to have larger value than S1. Since S1 diverges, this sequence must diverge too.