Question

Tolong dijawab nomor 7

Answer 1

Verified answer

Un = bn + a - b
U5 = 5b + a - b
7    = 4b + a

Un = bn + a - b
U8 = 8b + a - b
13 = 7b + a

  7 = 4b + a
13 = 7b + a
----------------- -
-6 = -3b
 b = -6/-3
 b = 2

7 = 4b + a
7 = 4(2) + a
7 = 8 + a
a = 7 - 8
a = -1

  Un = bn + a - b
U20 = 2(20) + (-1) - 2
        = 40 - 3
        = 37 (B)

Answer 2

U5 = 7
u8 = 13

ditanya u20

un = a+(n-1)b

u5 = a+(5-1)b = a+4b
jadi u5 = a + 4b

u8 = a+(8-1)b = a + 7b
jadi u8 = a + 7b

di eliminasi

a + 4b = 7
a + 7b = 13
dikurangi

-3b = -6
b = 2

subsitusikan
a + 4(2) = 7
a + 8 = 7
a = -1

U20 = a + (20-1)b
U20 = -1 + 19(2)
U20 = 37