1^0 + 2^0 + 3^0 + 4^0 + 5^0 + 6^0 + 7^0 + 8^0 + 9^0 = 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 = 1 × 9 = 9
(1 is the number of multiplicative identity, so n × 1 = n; notice that there are 9 1's!)
The caret (^) is the symbol of exponentiation. Raising a non-zero number to the power of zero(0) always gives you 1.
You can only pick counting numbers to be x in this summation formula because 1 is the number below the sigma, to the right of the small n & equal sign. All positive integers are counting numbers. (By the way, zero(0) isn't a counting number because it's neither positive nor negative; it's neutral)
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© Derek Cumberbatch