Tolong bantu jawab pakai cara!

1. a=8
r=U2-U1
r=6-8
r=-2
a+(n-1)b
8+(10-1)-2
8+(9.-2)
8+(-18)
U10= -10

2. a/U1=2
U7=20
a+(n-1)b
U1=a+(1-1)b=2
U7=a+(7-1)b=20
U7=a+6b=20
U1=a+0  =2
          6b =20-2
          6b =18:6
           b  = 3
a+(n-1)b
U20=2+(20-1)3
U20=2+(19.3)
U20=2+57
U20=59

3.U3=7
U11=47
a+(n-1)b
U3  =a+(3-1)b  =7
U11=a+(11-1)b=47
U11=a+10b=47
U3  =a+2b  =7
       10b-2b = 47-7
             8b  = 40
               b  = 40:8
               b  = 5
a+2b =7
a+2.5=7
a+10 =7
      a = -10+7
      a = -3
Un=a+(n-1)b
U101= -3+(101-1)5
U101= -3+(100.5)
U101= -3+500
U101= 497

semoga mudeng ya hehe