Math, asked by akhidevalla, 1 month ago

Q. For n=1,2,3,4....
, Xn = 1/5(n+3)(n+4) then what is the value
of 1/X1 + 1/X2 +.. +1/X996 ?​

Answers

Answered by amitnrw
1

Given :   For n=1,2,3,4....

Xₙ  = (1/5) (n + 3) (n + 4)

To Find :   1/X₁ + 1/X₂ +.. +1/X₉₉₆

Solution:

1/X₁  = 5/{ (1 + 3) (1 + 4) }  = 5/(4 * 5)

1/X₂ = 5/{ (2 + 3) (2 + 4) }  = 5/(5 * 6)

1/X₉₉₆ = 5/{ (999 + 3) (999 + 4) }  = 5/(999 * 100)

1/X₁ + 1/X₂ +.. +1/X₉₉₆

=   5/(4 * 5)  +  5/(5 * 6) + __________+  5/(999 * 100)

= 5 (  1/(4 * 5)   + 1/(5 * 6)  +  _______________1/(999*100))

= 5 (   (1/4  - 1/5) + (1/5 - 1/6)  + ________+(1/998 - 1/999)  +( 1/999 - 1/1000))

=5 ( 1/4 -  1/1000)

= 5( 996/1000)

=  4980/1000

= 498/100

= 4.98

1/X₁ + 1/X₂ +.. +1/X₉₉₆ = 4.98

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