1\(5.6)+1\(5.6.7) + 1\(5.6.7.8)+ .

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  • Thread starter Thread starter ashrafmod
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SUMMARY

The discussion focuses on the mathematical series represented by the expression 1(5.6) + 1(5.6.7) + 1(5.6.7.8) and its transformation into a factorial series. The rewritten form is \(\frac{1}{5*6}+\frac{1}{5*6*7}+\frac{1}{5*6*7*8} = \frac{4!}{6!}+\frac{4!}{7!}+\frac{4!}{8!}\), which simplifies to \(4! \cdot \left(\sum_{n=0}^{\infty}\frac{1}{n!}\right) - 4! \cdot \left(\sum_{n=0}^{5}\frac{1}{n!}\right)\). The hint provided relates to the exponential function \(e^x = \sum_{n=0}^{\infty} \frac{x^n}{n!}\), suggesting a connection to series expansion and convergence.

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ashrafmod
1\(5.6)+1\(5.6.7) + 1\(5.6.7.8)+.....

1\(5.6)+1\(5.6.7)+1\(5.6.7.8)+.....
 
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Well, rewrite this as:
[tex]\frac{1}{5*6}+\frac{1}{5*6*7}+\frac{1}{5*6*7*8}++++=\frac{4!}{6!}+\frac{4!}{7!}+\frac{4!}{8!}+++=4!*(\sum_{n=0}^{\infty}\frac{1}{n!})-4!*(\sum_{n=0}^{5}\frac{1}{n!})[/tex]
see if you can get somthing out of this.
 
Hint:

[tex]e^x = \sum _{n=0} ^{\infty} \frac{x^n}{n!}[/tex]
 

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