00:01
We're being asked to write our sum using summation notation.
00:05
So to do this, let's look at our very last term.
00:08
Well, it looks like they took an expression and substituted six in place of k, because we're going to write our formula in terms of k.
00:15
So it's almost like we have negative 1 to the k power times 1 over 3 to the k.
00:21
Well, let's see if this would work.
00:23
Well, if i substituted 1 in place a k, thinking that might give me my first term, i would have negative 1 to the first times 1 over 3 to the first.
00:33
However, negative 1 to the 1 is negative 1, and then 3 to the 1st is 1, so i'd have 1 3rd, which is equal to negative 1 3rd.
00:42
Well, if you notice, this actually gives us our second term...