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Dari barisan aritmetika diketahui U3​ = 18 dan  U7​ = 38. Jumlah 24 suku pertama adalah...

Pertanyaan

D a r i space b a r i s a n space a r i t m e t i k a space d i k e t a h u i space U subscript 3 space equals space 18 space d a n space space U subscript 7 space equals space 38. space J u m l a h space 24 space s u k u space p e r t a m a space a d a l a h...

  1. 786

  2. 1.248

  3. 1.572

  4. 3.144

H. Eka

Master Teacher

Mahasiswa/Alumni Universitas Pendidikan Indonesia

Jawaban terverifikasi

Pembahasan

P a d a space b a r i s a n space a r i t m e t i k a  U subscript n space equals space a space plus space left parenthesis n minus 1 right parenthesis b  S subscript n space equals space n over 2 left parenthesis 2 a space plus space left parenthesis n minus 1 right parenthesis b right parenthesis  S e h i n g g a  U subscript 3 space equals space a plus 2 b space equals space 18 space... left parenthesis i right parenthesis  U subscript 7 space equals space a space plus space 6 b space equals space 38 space... left parenthesis i i right parenthesis    D e n g a n space e l i m i n a s i comma space m a k a space d a p a t space d i k e t a h u i space n i l a i space a space d a n space b.  a space plus space 2 b space equals space 18  a space plus space 6 b space equals space 38 space space minus  _ _ _ _ _ _ _ _ _ _ _  space space space space space minus 4 b space equals negative 20  space space space space space space space space space space space b space equals 5  A k i b a t n y a  a space plus space 2 b space equals space 18 space m e n j a d i space a space plus space 2 left parenthesis 5 right parenthesis space equals space 18 space left right arrow space a space equals space 8    J a d i comma space S subscript 24 space equals space 24 over 2 open parentheses 2 open parentheses 8 close parentheses plus 23 open parentheses 5 close parentheses close parentheses  space space space space space space space space space space space space space space space space space space equals space 12 open parentheses 16 plus 115 close parentheses  space space space space space space space space space space space space space space space space space space equals space 12 space x space 131  space space space space space space space space space space space space space space space space space space equals space 1.572

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Suku ke-3 dan suku ke-7 barisan aritmetika berturut-turut 10 dan 22. Jumlah 30 suku pertama barisan tersebut adalah ....

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