bantu ngerjainnya ya.. makasih kak

U11 = S11 - S10
U11 = 286 - 205
U11 = 81

[tex]s11 = \frac{11}{2} (2a + (11 - 1)b \\ 286 \times 2 = 11(2a + 10b) \\ 572 = 22a + 110b[/tex]

[tex]s10 = \frac{10}{2} (2a + (10 - 1)b) \\ 205 = 5(2a + 9b) \\ 205= 10a + 45b[/tex]

22a + 110b = 572 |5|
10a + 45b = 205 |11|
_________________
110a + 550b = 2860
110a + 495b = 2255
_________________-
55b = 605
b = 605/55
b = 11

10a + 45b = 205
10a + 45(11) = 205
10a + 495 = 205
10a = 205 - 495
10a = -290
a = -290/10
a = -29

u11 = -29 + (11 -1) 11
u11 = -29 +110
u 11 = 81


jawabannya d