Find x_1+x_3+x_5+--------+x_999

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In summary, the given expression "Find x_1+x_3+x_5+--------+x_999" involves adding all odd numbers from x_1 to x_999. To solve this, we can either find the value of each term and add them together, or use the formula (n/2)(2a + (n-1)d). It can also be written in sigma notation as ∑_(i=1)^999 x_(2i-1). If x_1 = 1 and x_999 = 999, the value of the expression is 250,000. This type of expression has various real-life applications in mathematics, physics, computer programming, and financial calculations.
  • #1
Albert1
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$x_1+x_2=x_2+x_3=x_3+x_4=x_4+x_5=--------=x_{998}+x_{999}=1$

$x_1+x_2+x_3+x_4+x_5+--------+x_{999}=999$

find :

$x_1+x_3+x_5+x_7+---+x_{999}=?$
 
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  • #2
Albert said:
$x_1+x_2=x_2+x_3=x_3+x_4=x_4+x_5=--------=x_{998}+x_{999}=1$

$x_1+x_2+x_3+x_4+x_5+--------+x_{999}=999$

find :

$x_1+x_3+x_5+x_7+---+x_{999}=?$

Given
$x_1+x_2=x_2+x_3=x_3+x_4=x_4+x_5=\cdots=x_{998}+x_{999}=1\cdots(1)$
$x_1+x_2+x_3+x_4+x_5+\cdots+x_{999}=999\cdots(2)$
we have $x_1+x_2=x_2+x_3$ => $x_1= x_3$ ( from (1)
proceeding this way
$x_1 = x_3 = x_ 5 = \cdots = x_{999}\cdots(3)$
and similarly
$x_2 = x_4 = x_ 6 =\cdots = x_{998}\cdots(4)$
further from given relations
$x_1+ x_2 = 1\cdots(5) $ (from(1)
and $500x_1 + 499x_2 = 999\cdots(6) $ from (2), (3) and (4)
multiply (5) by 499 and subtract from (6) giving
$x_1 = 500$
so $x_1+x_3+x_5+x_7+---+x_{999}=500^2 = 250000$
 

Related to Find x_1+x_3+x_5+--------+x_999

1. What is the pattern in "Find x_1+x_3+x_5+--------+x_999"?

The pattern in this expression is that we are adding all odd numbers from x_1 to x_999. This can also be written as the sum of all odd terms in the series x_1 to x_999.

2. How do we solve "Find x_1+x_3+x_5+--------+x_999"?

To solve this expression, we need to first find the value of x_1, x_3, x_5, and so on until x_999. Then, we can simply add all these values together to get the final answer. Alternatively, we can use the formula (n/2)(2a + (n-1)d) where n is the number of terms, a is the first term, and d is the common difference to find the sum of the series.

3. Can we rewrite "Find x_1+x_3+x_5+--------+x_999" as a sigma notation?

Yes, we can rewrite this expression in sigma notation as ∑_(i=1)^999 x_(2i-1), where i represents the term number and 2i-1 represents the odd term in the series.

4. What is the value of "Find x_1+x_3+x_5+--------+x_999" if x_1 = 1 and x_999 = 999?

If x_1 = 1 and x_999 = 999, then the value of the expression would be 250,000. This can be calculated by using the formula (n/2)(a + l) where n is the number of terms, a is the first term, and l is the last term in the series.

5. What real-life applications does "Find x_1+x_3+x_5+--------+x_999" have?

This type of expression is commonly used in mathematics and physics to find the sum of a series of terms with a specific pattern. It can also be used in computer programming to calculate the sum of odd numbers or in financial calculations to find the total cost or revenue over a period of time.

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