tentukan unsur yang diminta dari deret aritmatika berikut 1. a=2, s22=737, b= 2. b=5, u10=46, s15= 3. u4=9, u7=18, s10=
Matematika
dita186
Pertanyaan
tentukan unsur yang diminta dari deret aritmatika berikut
1. a=2, s22=737, b=
2. b=5, u10=46, s15=
3. u4=9, u7=18, s10=
1. a=2, s22=737, b=
2. b=5, u10=46, s15=
3. u4=9, u7=18, s10=
1 Jawaban
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1. Jawaban Dimasalfan04
Sn = 1/2n [ 2a + ( n – 1 ) b ] <<== acuan
Un = a + (n-1) b <<==== acuan
1. a = 2 , S22 = 737 , b =....???
Sn = 1/2n [ 2a + ( n – 1 ) b ]
s22 = 22/2 [ 2 (2) + (21) b ]
737 = 11 [ 4 + 21 b ]
737 / 11 = 4 + 21 b
21 b = 67 - 4
b = 63/21
b = 3 ===>>> lets Rock
2. b = 5 , u10 = 46 , s15..???
Un = a + (n-1) b
U10 = a + (9) 5
46 = a + 45
a = 1 <<====
Sn = 1/2n [ 2a + ( n – 1 ) b ]
s15 = 15/2 ( 2(1) + 14 (5) )
s15 = 15/2 ( 72 )
s15 = 540 <<==== Rock It
3. u4 = 9 , u7 = 8 , s10...????
U4 = 9
a + 3b = 9
a = 9 - 3b ==>>> acuan
U7 = 8
a + 6b = 8
9 - 3b + 6b = 8
3b = 8 - 9
b = -1/3 ==>_ subs ke nilai U4 utk nilai a
a + 3b = 9
a + 3 (-1/3) = 9
a - 1 = 9
a = 10 <<====
Sn = 1/2n [ 2a + ( n – 1 ) b ]
S10 = 10/2 [2 (10) + 9 (-1/3) ]
S10 = 5 [ 20 - 3 ]
s10 = 5 ( 17 )
s10 = 85 ===>__ Rock Finish