Answer
The \[{{n}^{th}}\]term of given arithmetic sequence is\[{{a}_{n}}=200+(n-1)(-20)\]. The twentieth term of the arithmetic sequence is\[-180\].
Work Step by Step
Hence, the general term for the given arithmetic sequence is
\[\begin{align}
& {{a}_{n}}={{a}_{1}}+\left( n-1 \right)d \\
& \,\,\,\,\,\,=200+(n-1)(-20) \\
\end{align}\]
To find the twentieth term put \[n=20\] in the above formula, to get
\[\begin{align}
& {{a}_{20}}={{a}_{1}}+\left( 20-1 \right)d \\
& =200+19\cdot \left( -20 \right) \\
& =200-380 \\
& =-180
\end{align}\]
The \[{{n}^{th}}\]term of given arithmetic sequence is\[{{a}_{n}}=200+(n-1)(-20)\]. The twentieth term of the arithmetic sequence is\[-180\].
