4) Arithmetic series is typically: a, a+d, a+2d, ..., a+(n-1)d, ... where n indicates Tn and d is the common difference, a is the first term.
Therefore, T2=a+d=-2 and T5=a+4d=-8. T5-T2=3d=-6, d=-2, a=0.
Series is 0, -2, -4, -6, -8, -10, -12, -14, ... so T8=-14.
Using the formula a+(n-1)d we also get 0+7(-2)=-14 for T8.
S6=0-2-4-6-8-10=-30.
We can also use the formula -2n(n+1)/2=-n(n-1)=(-6)(5)=-30 for S6.