Question 979036
Geometric?  MAYBE an alternating sequence.


{{{system(x/(-2/7)=r,-(2/7)/x=r)}}}


{{{r=-7x/2,r=-2/(7x)}}}


both formulas for r must be true.
{{{-7x/2=-2/(7x)}}}
{{{7x/2=2/(7x)}}}
{{{7x*7x=2*2}}}
{{{x^2=(2*2)/(7*7)}}}
{{{x=0+- 2/7}}}-------either or any of these can work.