we can check if a given sequence is geometric or not by checking the terms present in it ,
Let us find ratio of each term with it's previous term
if that ratio comes out same for every two consecutive terms then it is a geometric sequence , otherwise it is not geometric sequence .
Let us work on first one : given is : -1,1,-1,1.............
second term/ first term = 1/-1 = -1
third term/ second term = -1/1 = -1
fourth term / third term = 1/-1 = -1
fifth term/ fourth term = -1/1 = -1
because that ratio is same so it is a geometric sequence .
* let us now work with second sequence .
eE
second term/ first term = -6/-2 = 3
third term/ second term = -18/ -6 = 3
fourth term / third term = -54 / -18 = 3
hence this is also geometric sequence .
Answer : both are geometric sequence .