====== Question 13 and 14, Exercise 4.1 ======
Solutions of Question 13 and 14 of Exercise 4.1 of Unit 04: Sequence and Series. This is unit of Model Textbook of Mathematics for Class XI published by National Book Foundation (NBF) as Federal Textbook Board, Islamabad, Pakistan. 


=====Question 13=====
Find the indicated term of the sequence. $a_{n}=(3 n+4)(2 n-5) ; a_{7}$

** Solution. **

Do yourself.


=====Question 14=====
Find the indicated term of the sequence. $a_{n}=(-1)^{n-1}(3.4 n-17.3) ; a_{12}$

** Solution. **

Given:
$$a_n = (-1)^{n-1}(3.4n - 17.3).$$
Then
\begin{align*}
a_{12} &= (-1)^{12-1}(3.4 \cdot 12 - 17.3) \\
&= (-1)^{11}(40.8 - 17.3) \\
&= (-1)^{11}(23.5) \\
&= -23.5
\end{align*}
Hence $a_{12} =-23.5 $ GOOD


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