SOLUTION: Simplify the following: <img src="https://i.ibb.co/MPfy9Qc/12.png" height="50px">

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Question 1205325: Simplify the following:

Found 3 solutions by ikleyn, math_tutor2020, Edwin McCravy:
Answer by ikleyn(52915) About Me  (Show Source):
You can put this solution on YOUR website!
.

The original expression is

    1%5E2%2F%282%2A1%29 + 3%5E2%2F%282%2A3%29 + 5%5E2%2F%282%2A5%29 + 7%5E2%2F%282%2A7%29 + . . . + 103%5E2%2F%282%2A103%29 = 


The common term is of the form  k%5E2%2F%282k%29 = k%2F2,  where k is an odd natural number.


Therefore, the sequence is reduced to 

    1%2F2 + 3%2F2 + 5%2F2 + 7%2F2 + . . . + 103%2F2 = %281%2F2%29%2A%281+%2B+3+%2B+5+%2B+7+%2B+ellipsis+%2B+103%29.


The sum  1 + 3 + 5 + 7 + . . . + 103 is equal to  %28%281%2B103%29%2F2%29%2A52 = 52%5E2.


Therefore, the original expression is  %281%2F2%29%2A52%5E2 = 52*26 = 1352.


ANSWER.  1%5E2%2F%282%2A1%29 + 3%5E2%2F%282%2A3%29 + 5%5E2%2F%282%2A5%29 + 7%5E2%2F%282%2A7%29 + . . . + 103%5E2%2F%282%2A103%29 = 1352.

Solved.



Answer by math_tutor2020(3817) About Me  (Show Source):
You can put this solution on YOUR website!

Tutor @ikleyn probably has the most efficient pathway, but here's another approach.

The pattern in the numerator (1^2,3^2,5^2,7^2,...) follows the sequence (2k-1)^2 where k is an integer and k = 1 is the starting index.
Note how 1,3,5,7,... is an arithmetic sequence.
The highest that k goes is k = 52 because 2k-1 = 2*52 - 1 = 103.

The pattern in the denominator (2,6,10,14,...) is also arithmetic and follows the sequence 4k-2
Note that 4k-2 = 4*52 - 2 = 206.

Each term can be written of the form

We're tasked to find the summation sum%28%28k-1%2F2%29%2Ck=1%2C52%29

Use these summation identities
sum%28%28A%2BB%29%2Ck=1%2Cn%29+=+%28sum%28A%2Ck=1%2Cn%29%29%2B%28sum%28B%2Ck=1%2Cn%29%29
and
sum%28k%2Ck=1%2Cn%29+=+n%28n%2B1%29%2F2
and

to have the following steps



sum%28%28k-1%2F2%29%2Ck=1%2C52%29=52%2A%2852%2B1%29%2F2%2B%28-1%2F2%29%2A52

sum%28%28k-1%2F2%29%2Ck=1%2C52%29=1352

Therefore,


Answer by Edwin McCravy(20065) About Me  (Show Source):
You can put this solution on YOUR website!
How about this way?:



0.5 + 1.5 + 2.5 + 3.5 + ... + 51.5 = 

The sum of the whole parts:

0 + 1 + 2 + 3 + ... + 51 = %2851%29%2852%29%2F2 = 1326

PLUS

the sum of the 52 decimal parts of 0.5 each:

52 x 0.5 = 26

EQUALS

1352

Edwin