Test: Arithmetic Series I - Ambitious

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Question 1:   Find the formula of the n-th term of an arithmetic progression $\text{\hspace{0.17em}}\left({b}_{n}\right)\text{\hspace{0.17em}}$ :
${b}_{n}=a-2n+1$
${b}_{n}=a+2n+1$
${b}_{n}=a-2n+4$
Question 2:   In the arithmetic progression ($\text{\hspace{0.17em}}{a}_{n}\text{\hspace{0.17em}}$ ): $\text{\hspace{0.17em}}{a}_{1}=1;\text{\hspace{0.17em}}d=2.5\text{\hspace{0.17em}}$ . Is $\text{\hspace{0.17em}}13.5\text{\hspace{0.17em}}$ a term of this progression? If yes, find its number.
$13.5\text{\hspace{0.17em}}$ is not a term of this progression
$n=6$
$n=5$
$n=13$
Question 3:   Find the initial term of the arithmetic sequence ($\text{\hspace{0.17em}}{a}_{n}\text{\hspace{0.17em}}$ ), if .
${a}_{1}=19$
${a}_{1}=26$
More data is needed
${a}_{1}=23$
Question 4:   What is the number of the first positive term of an arithmetic sequence ($\text{\hspace{0.17em}}{a}_{n}\text{\hspace{0.17em}}$ ): $-10.2;-9.5;-8.8;$…?
$n=16$
$n=10$
$n=15$
$n=14$
Question 5:   Find the first negative term of an arithmetic sequence ($\text{\hspace{0.17em}}{a}_{n}\text{\hspace{0.17em}}$ ): $\text{\hspace{0.17em}}7.2;\text{\hspace{0.17em}}6.6;\text{\hspace{0.17em}}6\text{\hspace{0.17em}}$ .
$-0.6$
$-0.1$
$-1.8$
$-1.2$
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