- #1
Jhonny
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Hello, I can not find the way to solve the following equation:
sum of k^2 f(k) from k=1 to n.
In Particular, k^2 * (1/k)
sum of k^2 f(k) from k=1 to n.
In Particular, k^2 * (1/k)
That's not what I suggested.Jhonny said:I already tried that, but it didn't work.
For example:
∑{k=1,n} [k·f(k)] = 1·f(1) + 2·f(2) + 3·f(3) + ... + n·f(n) = ∑{k=1,n} [ ∑{j=k,n} [f(j)] ]
But,
∑{k=1,n} [k^2·f(k)] = 1·f(1) + 4·f(2) + 9·f(3) + ... + n^2·f(n) ≠ ∑{k=1,n} [ ∑{j=k,n} ∑{i=j,n}[[f(i)]] ]
Right, as you start the multiplications with j=k, not with 1. There is a way to avoid that.Jhonny said:It seems to be that:
Although: ∑{k=1,n} [k·f(k)] = ∑{k=1,n} [ ∑{j=k,n} [f(j)] ] holds,
∑{k=1,n} [ ∑{j=k,n} [j*f(j)] ] = ∑{k=1,n} [ ∑{j=k,n} ∑{i=j,n}[[f(i)]] ] does not hold.
mfb said:That's not what I suggested.
Right, as you start the multiplications with j=k, not with 1. There is a way to avoid that.
As you have already been told, you are not "solving" these summations. Instead, you are writing them in a different form.Jhonny said:How can I solve: ∑{k=1,n} [k^2· 2^(-k)]
veronica100 said:hello,
what is sigma properties??
I have changed the title of this thread to "Summation properties".mfb said:Sigma (##\Sigma##) is the greek symbol used for sums. The question is about properties of sums.
What a pitty. ∑ properties would have been far more interesting.Mark44 said:I have changed the title of this thread to "Summation properties".
Are you referring to sigma-algebras (##\sigma-\text{algebras}##) and the like? If so, lowercase ##\sigma## (sigma) is used.fresh_42 said:What a pitty. ∑ properties would have been far more interesting.
I meant hyperons and yes, it was meant to be both funny and a food for thought. But hey, I'm new and I'am trying to get used to the language here. Jokes don't seem to rank very high. Ok, lesson learned.Mark44 said:Are you referring to sigma-algebras (##\sigma-\text{algebras}##) and the like? If so, lowercase ##\sigma## (sigma) is used.
In any case, and interesting or not, the title now reflects what the OP asked.
Summation properties refer to the rules and techniques used to solve equations that involve summation, also known as a series. These properties help simplify the process of solving equations with multiple terms by providing guidelines for manipulating and combining them.
Summation properties are typically used when solving equations that involve multiple terms, especially those in the form of a series. If you encounter an equation with a summation symbol (∑), it is a good indication that summation properties will be necessary to solve it.
Some of the most common summation properties include the distributive property, the commutative property, the associative property, and the identity property. These properties allow you to manipulate and rearrange the terms within a summation to simplify the equation and ultimately solve it.
First, identify which properties are applicable to the equation. Then, use these properties to rearrange the terms in the summation and simplify the equation. Finally, solve for the variable by performing the necessary operations on both sides of the equation.
Some tips for using summation properties effectively include practicing with various types of equations, familiarizing yourself with the different properties and their applications, and checking your work by plugging in values for the variable to ensure that the equation is satisfied.