Answer:
81x-79
Step-by-step explanation:
I'm going to assume that the last expression is 11x-19 instead of 11.-19. First things first, we find a pattern in this arithmetic sequence. We can see that each expression adds 7x-7 to get the next term. We then can create a formula for this. Since the first expression is -3x-5, and it repeadetly adds 7x-7, we can get (-3x-5)+(7x-7). But we're not done here yet.
We can notice that the first term doesn't add any 7x-7 to it. The second term adds 1 of the (7x-7)'s, and the third term adds 2. The relationship between the term number and the number of (7x-7)'s added to -3x-5 always subtracts one. I'm going to add t as #term to show that t-1 is the number of (7x-7)'s that are added to (-3x+5)So, we can add a (t-1) to this expression to get (-3x+5)+(7x-7)* (t-1). Now that we have the formula, we insert 13 as t into the equation and simplify.
=(-3x+5)+(7x-7)*12
=(-3x+5)+84x-84
=81x-79
Note that this is just my way of solving these types of things, but an alternative way is to keep adding 7x-7 to the sequence until you get to the 13th expression. That works too. Hope this helps! Good luck! (I'm not really sure if this answer is correct, but please let me know if it is wrong)
