In Exercises 16–18, find the indicated term of the arithmetic seq...

Question

In Exercises 16–18, find the indicated term of the arithmetic sequence with first term, , and common difference, d. Find a12 when a1 = -8, d = -2

Accepted Answer

Welcome back. I'm so glad you're here. We know a few things about an arithmetic sequence. We know that the common difference D equals negative seven. We know that the value of the first term, one is five and we're trying to find a sub 17 or the value of the 17th term. Well we recall from previous lessons, we've got a formula for finding the value of any term which is a sub N. And is telling us that. And term we're looking for what term. And so a sub N equals a sub one. The value of the first term plus n minus one times D. And again the term we're looking for is the 17th term. So a sub 17 equals a sub one plus 17 minus one time's D. What do we know? We can fill in a sub one which is five and we can fill in D. Which is negative seven. And we know that 17 minus one is 16 and now we'll just do the algebra 16 times negative seven is negative 112. So five minus 112. Well a sub 17 the value of the 17th term in this arithmetic sequence is negative 107. We look at our answer choices and that is answer choice. A well done. We'll catch you on the next one

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