Geometric progression is a, ar, ar2, ar3, ..., where a is the first term T1, and r is the common ratio.
T1+T2=-1, T3+T4=-4 so a+ar=-1=a(1+r); ar2+ar3=-4=ar2(1+r).
ar2(1+r)/(a(1+r))=-4/-1=r2 so r2=4, r=2 (r>0).
a(1+r)=3a=-1, a=-⅓.
GP=-⅓, -⅔, -1⅓, -2⅔, -5⅓, ... T1+T2=-⅓-⅔=-1; T3+T4=-1⅓-2⅔=-4.