1)a3=8,d=3,a1-?2) a1=10, d=4, n=113)a3=25, a10=-3,a1-?, d-?4)a1=3, a2=7, a51-?5)a11=23,...

Question

1)a3=8,d=3,a1-?
2) a1=10, d=4, n=11
3)a3=25, a10=-3,a1-?, d-?
4)a1=3, a2=7, a51-?
5)a11=23, a21=43,a51-?
6)a1=-5,d=4,S18-?

Answer 1

1) a1=a3-2d=8-6=2
2) a11=a1+10d=10+40=50
3) d=(a10-a3)/7=(-3-25)/7=-4. a1=a3-2d=25-(-8)=33
4)d=a2-a1=7-3=4, a51=a1+50d=3+50*4=253
5) d=(a21-a11)/10=(43-23)/10=2. a51=a21+30d=43+60=103
6) S18=(a1+a18)/2*18. a18=a1+17d=-5+17*4=63. S18=(-5+63)/2*18=522