Let's create a list of the first n positive integers:
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10] [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] |
Now let's add them up and square the sum.
In other words, we are finding (1 + 2 + 3 + ... + n)^2.
3025 3025 |
Expressed in sigma notation, we have just found (\sum_{x = 1}^{n}x)^2.
Now let's find the cubes of the original n terms.
[1, 8, 27, 64, 125, 216, 343, 512, 729, 1000] [1, 8, 27, 64, 125, 216, 343, 512, 729, 1000] |
And now let's add up the cubes. In other words, we are finding 1^3 + 2^3 + 3^3 + ... + n^3.
3025 3025 |
Expressed in sigma notation, we have found \sum_{x = 1}^{n}x^3
Experiment with different values of n and verify whether or not
(1 + 2 + 3 + ... + n)^2 = 1^3 + 2^3 + 3^3 + ... + n^3,
or (\sum_{x = 1}^{n}x)^2 = \sum_{x = 1}^{n}x^3.
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 55 3025 [1, 8, 27, 64, 125, 216, 343, 512, 729, 1000] 3025 [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 55 3025 [1, 8, 27, 64, 125, 216, 343, 512, 729, 1000] 3025 |
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