Math

QuestionCalculate the sum: n=26n1n(n+1)\sum_{n=2}^{6} \frac{n-1}{n(n+1)}.

Studdy Solution

STEP 1

Assumptions1. We are given a finite series that starts at n= and ends at n=6. . The general term of the series is n1n(n+1)\frac{n-1}{n(n+1)}.

STEP 2

We need to calculate the sum of the series. The sum of a series is calculated by adding up all the terms of the series.
n=26n1n(n+1)=212(2+1)+1(+1)+414(4+1)+515(5+1)+616(6+1)\sum_{n=2}^{6} \frac{n-1}{n(n+1)} = \frac{2-1}{2(2+1)} + \frac{-1}{(+1)} + \frac{4-1}{4(4+1)} + \frac{5-1}{5(5+1)} + \frac{6-1}{6(6+1)}

STEP 3

implify each term in the series.
n=26n1n(n+1)=16+212+320+30+542\sum_{n=2}^{6} \frac{n-1}{n(n+1)} = \frac{1}{6} + \frac{2}{12} + \frac{3}{20} + \frac{}{30} + \frac{5}{42}

STEP 4

Further simplify each term in the series.
n=26n1n(n+1)=16+16+320+215+42\sum_{n=2}^{6} \frac{n-1}{n(n+1)} = \frac{1}{6} + \frac{1}{6} + \frac{3}{20} + \frac{2}{15} + \frac{}{42}

STEP 5

Calculate the sum of the series by adding all the terms together.
n=2n1n(n+1)=1+1+320+215+542=13+320+215+542\sum_{n=2}^{} \frac{n-1}{n(n+1)} = \frac{1}{} + \frac{1}{} + \frac{3}{20} + \frac{2}{15} + \frac{5}{42} = \frac{1}{3} + \frac{3}{20} + \frac{2}{15} + \frac{5}{42}

STEP 6

To add these fractions, we need to find a common denominator. The least common multiple of3,20,15, and42 is420.
13+320+215+542=140420+63420+56420+50420\frac{1}{3} + \frac{3}{20} + \frac{2}{15} + \frac{5}{42} = \frac{140}{420} + \frac{63}{420} + \frac{56}{420} + \frac{50}{420}

STEP 7

Add the fractions together.
140420+63420+56420+50420=309420\frac{140}{420} + \frac{63}{420} + \frac{56}{420} + \frac{50}{420} = \frac{309}{420}

STEP 8

implify the fraction to its lowest terms.
309420=103140\frac{309}{420} = \frac{103}{140}The sum of the series n=26n1n(n+1)\sum_{n=2}^{6} \frac{n-1}{n(n+1)} is 103140\frac{103}{140}.

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