Question

S=(1)/(1x3x5)+(1)/(1x4)+(1)/(3x5x7)+(1)/(4x7)+(1)/(5x7x9)+(1)/(7x10)++ upto 20th term. Find the value of s

Answer 1

Step-by-step explanation:

Here series is....

1/(1*4)+1/(4*7)+1/(7*10)+.....

Here there is a difference of 3 between (1,4) , (4,7), (7,10)....

So we multiply and devide this series with 3 so we get,

(1/3)*(3/1*4 + 3/4*7 +......)

= (1/3)*(1-(1/4) + (1/4)-(1/7) +......)

= (1/3)*1

= 1/3

So, the answer is 1/3.

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