Answer:
-1
Step-by-step explanation:
[tex]a_1=7\\a_2=-7\\a_3=7\\a_4=-7\\\vdots\\a_n=(-1)^{n+1}(7)\\\\\text{The common ratio is}\ r=-1[/tex]
[tex]r=\dfrac{a_{n+1}}{n}[/tex]
[tex]\dfrac{a_4}{a_3}=\dfrac{-7}{7}=-1\\\\\dfrac{a_3}{a_2}=\dfrac{7}{-7}=-1\\\\\dfrac{a_2}{a_1}=\dfrac{-7}{7}=-1[/tex]
