How do you expand #sum_(n=3)^7(n+4)#?

1 Answer
Truong-Son N.
May 4, 2016

This is just asking you to write out the sum of these terms.

Notice how #n# is in the lower bound and #n# is also a term in the argument. Then, that implies you will be substituting the #n# in the argument with #n in {3, 4, 5, 6, 7}#.

So:

#sum_(n=3)^(7) (n+4)#

#= (3+4) + (4+4) + (5+4) + (6+4) + (7+4)#

#= 7 + 8 + 9 + 10 + 11#

#= 15 + 19 + 11#

#= color(blue)(45)#

And indeed, Wolfram Alpha agrees.

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