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To write the formula for the nth term, you need to know the common difference and the first term of the sequence.
a_9=-18, a_(10)=-21
To begin, let's observe the given terms in the sequence to determine the value of the first term as well as the common difference.
6+(-3) →3+(-3) →0+(-3) →-3
We can use this information to write an equation for the nth term of the sequence.
Explicit equations for the nth term of an arithmetic sequence follow a certain format. a_n= a_1+( n-1) d In this form, a_1 is the first term in the sequence, d is the common difference, and n is the position of the desired term in the sequence. Using the common difference d= -3 and the first term a_1= 6, we can write and simplify the equation.
a_1= 6, d= -3
Distribute -3
Add terms
To find the value of the 9th and 10th term, we substitute n= 9 and n= 10 into this equation and solve for a_n.
| a_9 | a_(10) |
|---|---|
| 9-3* 9 | 9-3* 10 |
| 9-27 | 9-30 |
| -18 | -21 |