# Write an equation for the nth term of the arithmetic sequence: -3, -5, -7, -9, ...

Write an equation for the nth term of the arithmetic sequence: -3, -5, -7, -9, ...
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Ricky Lamb
The formula for an arithmetic sequence is ${a}_{n}={a}_{1}+\left(n-1\right)d$
where ${a}_{1}$ is the first term and d is the difference between terms.
In this case ${a}_{1}=-3$ and d=−2
${a}_{n}=-3+\left(n-1\right)\left(-2\right)=-3-2n+2=-2n-1$
${a}_{n}=-2n-1$