tolong kerjakan di atas

a. A= 6. B=3
Sn = 1/2 n [ 2a + ( n - 1 ) b ]
S10 = 1/2 10 [ 2. 6 + ( 18 - 1 ) 3 ]
S10 = 5 [ 12 + 17.3 ]
S10 = 5 [ 12 + 51 ]
S10 = 5. 63
S10 = 315

b. A = 5. B = 4
S20 = 1/2 20 [ 2. 5 + ( 20 -1 ) 4 ]
S20 = 10 [ 10 + 19.4 ]
S20 = 10 [ 10 + 76 ]
S20 = 10. 86
S20 = 860

c. A = -1. B = 4
S11 = 1/2 11 [ 2.-1 + ( 11 - 1 ) 4 ]
S11 = 5,5 [ -2 + 9.4 ]
S11 = 5,5 [ -2 + 36 ]
S11 = 5,5. 34
S11 = 187

d. kurang hafam, maaf

e. A= -3. B= 2
S18 = 1/2 18 [ 2.-3 + ( 18 - 1 ) 2 ]
S18 = 9 [ -6 + 17.2 ]
S18 = 9 [ -6 + 34 ]
S18 = 9. 28
S19 = 252

Maaf kalau Salah