Question

bantuu jawabb no 4 smaa 5 ya

pake cara

dikumpul besokk​

Answer 1

4. •U9 = a + (9-1)b

12 = a + 8b (i)

•U21 = a + (21-1)b

72 = a + 20b (ii)

Eliminasi pers. (i) dan (ii) :

a + 8b = 12

a + 20b = 72

__________-

-12b = -60

b = -60/-12

b = 5

Substitusi nilai b ke pers. (i)

a + 8b = 12

a + 8(5) = 12

a + 40 = 12

a = 12 - 40

a = -28

→ Maka jumlah 5 suku pertama adalah :

Sn = (n/2)(2a + (n-1)b)

S5 = (5/2)(2a + (5 - 1)b)

S5 = (5/2)(2(-28) + 4(5))

S5 = (5/2)(-56 + 20)

S5 = (5/2)(-36)

S5 = -90 (d.)

5. m = (y2 - y1)/(x2 - x1)

m = (7 - 4)/(3 - 1)

m = 3/2 (a.)