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# How do I write this as an expanded sum ? :?

4 ( )

∑ ( 2i² - 1 )

i = 1 ( )

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- sparkyLv 49 years agoFavorite Answer
start by replacing the "i" in the expression (2i² - 1) with 1, then 2, then so on until you get to 4. The start value and end value are indicated below and above the summation sign (and are called the lower and upper index of summation)

( 2(1)² - 1 ) + ( 2(2)² - 1 ) + ( 2(3)² - 1 ) + ( 2(4)² - 1 )

or: 1 + 7 + 17 + 31 if you simplify the terms

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