Question

Summation notation for -1+4-9+16-25+36

Answer 1

798?

Answer 2

Break it down, what do you notice about each of the numbers, for simplicity, lets only look at the numbers as if they were all positive,\[1,4,9,16,25,36=1^2,2^2,3^2,4^2,5^2,6^2\]now fill in the negatives and you'll notice something\[-1^2,2^2,-3^3,4^2,-5^2,6^2\]the negatives are only with the odd numbers, so we can do a little trick that you need to understand and remember
First write out the summation without the negatives\[\sum_{i=1}^{6}x^2\]Can you notice what you need to multiply by in order to get that alternative negative symbol?

Answer 3

\(\Huge -49\)