Q. Find the 100 th term of the arithmetic sequence −9,−19,−29,…Answer:
Arithmetic Sequence Formula: To find the 100th term of an arithmetic sequence, we use the formula for the nth term of an arithmetic sequence, which is an=a1+(n−1)d, where an is the nth term, a1 is the first term, n is the term number, and d is the common difference between the terms.
Identify First Term: First, identify the first term (a1) of the sequence. In this case, the first term is −9.
Determine Common Difference: Next, determine the common difference d of the sequence. The common difference is the difference between any two consecutive terms. Here, the second term is −19 and the first term is −9, so the common difference is −19−(−9)=−10.
Find 100th Term: Now, apply the formula to find the 100th term a100. We have a1=−9, n=100, and d=−10. Plugging these values into the formula gives us a100=−9+(100−1)(−10).
Calculate Inside Parentheses: Perform the calculation inside the parentheses first: 100−1=99.
Multiply by Common Difference: Now multiply 99 by the common difference, −10: 99×−10=−990.
Add First Term: Finally, add the first term to this product to find the 100th term: a100=−9+(−990)=−999.
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