00:01
We're being asked to write the formula to find the nth term of our given arithmetic sequence, negative 5, negative 7, negative 9, negative 11, negative 13, etc.
00:10
Well, remember, our general formula for this is a sub n is equal to a sub 1 plus the quantity of n minus 1 times d.
00:19
So, if we're trying to write the formula for this particular sequence, we need to know a sub 1 and we need to know d.
00:26
Well, remember, a sub 1 represents the first term in the sequence.
00:30
Which in this case is negative 5.
00:33
And d represents our common difference, which is the constant that's getting added to get from one term to the next.
00:40
Well, in this case, you'll notice that we're adding a negative 2 to get from one term to the next.
00:46
So what that tells us is that d will be equal to negative 2.
00:51
Now we simply need to substitute negative 5 in for a sub 1 and negative 2 in for d in our formula...