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The nth term of a sequence is given. Find the first 4 terms; the 10 th term, \(a_{10} ;\) and the 15 th term, \(a_{15},\) of the sequence. $$ a_{n}=(-1)^{n} n^{2} $$

Short Answer

Expert verified
The first 4 terms are -1, 4, -9, and 16. a_{10} = 100 and a_{15} = -225.

Step by step solution

01

- Find the 1st term (n=1)

Substitute n = 1 into the given formula a_n = (-1)^n n^2. This gives us: a_1 = (-1)^1 * 1^2 = -1.
02

- Find the 2nd term (n=2)

Substitute n = 2 into the formula a_n = (-1)^n n^2. This gives us: a_2 = (-1)^2 * 2^2 = 4.
03

- Find the 3rd term (n=3)

Substitute n = 3 into the formula a_n = (-1)^n n^2. This gives us: a_3 = (-1)^3 * 3^2 = -9.
04

- Find the 4th term (n=4)

Substitute n = 4 into the formula a_n = (-1)^n n^2. This gives us: a_4 = (-1)^4 * 4^2 = 16.
05

- Find the 10th term (n=10)

Substitute n = 10 into the formula a_n = (-1)^n n^2. This gives us: a_{10} = (-1)^{10} * 10^2 = 100.
06

- Find the 15th term (n=15)

Substitute n = 15 into the formula a_n = (-1)^n n^2. This gives us: a_{15} = (-1)^{15} * 15^2 = -225.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

nth term calculation
Finding the nth term of a sequence is about determining the value of the sequence at position n. This can be done by using a sequence formula.
In the given problem, the sequence formula is \(a_n = (-1)^n n^2\).
To find any term in the sequence, we simply substitute the value of n into the formula.
  • Example: For the 10th term, we substitute n = 10 to get \(a_{10} = (-1)^{10} \times 10^2 = 100\).
  • Example: For the 15th term, we substitute n = 15 to get \(a_{15} = (-1)^{15} \times 15^2 = -225\).
By following this process, we can find any desired term in the sequence.
The formula and our understanding of exponents guide us in calculating the correct value for each term.
sequence formula
A sequence formula is a rule that defines the nth term of a sequence. It uses variables and mathematical operations to show how sequence terms are determined.
For this exercise, the given sequence formula is \(a_n = (-1)^n n^2\).
This formula tells us several important things:
  • \

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Most popular questions from this chapter

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