Tentukan 20 suku pertama pada deret deret aritmetika berikut ini.c 1. 4+6+8+.... 2. 2+6+10+... 3. 10+9+8+.... 4. 36+34+32+... 5. 100+92+84+...

1 ) 4 + 6 + 8

Un. = a + ( n - 1 ) b

U20 = 4 + ( 20 - 1 ) 2

U20 = 4 + ( 19 ) 2

U20 = 4 + 38

U20 = 42

2 ) 2 + 6 + 10

Un. = a + ( n - 1 ) b

U20 = 2 + ( 20 - 1 ) 4

U20 = 2 + ( 19 ) 4

U20 = 2 + 76

U20 = 79

3 ) 10 + 9 + 8

U20 = 10 + ( 20 - 1 ) -1

U20 = 10 + ( 19 ) . -1

U20 = 10 + -19

U20 = -9

4 ) 36 + 34 + 32

U20 = 36 + ( 20 - 1 ) -2

U20 = 36 + ( 19 ) -2

U20 = 36 + ( -38 )

U20 = -2

5 ) 100 + 92 + 84

U20 = 100 + ( 20 - 1 ) -8

U20 = 100 + ( 19 ) . -8

U20 = 100 + ( -152 )

U20 = -52

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