1.-16+(-12)+(-8)+ ... U202.35+31+27... U31please answer...Thanks before.... Question from @muhammadridho

August 2018 2 58 Report

1.-16+(-12)+(-8)+ ... U20
2.35+31+27... U31

please answer...
Thanks before...

stevenwilliam73 1.
-16, -12, -8
deret aritmatika dengan beda 4
Un=a+(n-1)b
U20= (-16)+19*4
U20=60

2.
35, 31, 27
aritmatika dengan beda -4
U31=35+30*(-4)
U31= -85

1 votes Thanks 0

stevenwilliam73 Un -> suku ke-n SN -> jumlah semua suku

AndhitaPP jadi klo nyari urutan Un = a + (n-1)b klo nyari jumlah Sn = 1/2n {2a + (n-1)b}

stevenwilliam73 3+5+7... U20 U20 = 41 S20 = 440

stevenwilliam73 yap tepat

AndhitaPP thank you kakak

stevenwilliam73 kl pake logika tambahin ja 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 = 440

muhammadridho yg mna yg bner ni?440 atw 41?

AndhitaPP klo pertanyaan kakak hasilnya 41

muhammadridho THNKS

stevenwilliam73 U20 itu 41 bantuin dong jawaban terbaik butuh 2 lg :)

AndhitaPP Un = n{2a+(n-1)d}
2
1.) u20 = 20 { 2.-16 + (20 -1 ) . 4 }
2
= 10 ( -32 +9 . 4)
= 10 ( -32+36)
= 10 ( 4) = 40

2.) u31 = 31 {2.35 + (31 -1). -4
2
= 31 (70 +30 . -4 )
2
= 31.-50
2
= 31 . -25 = - 775
maaf klo salah,, sekian

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