Pertanyaan
pada deret geometri dketahui u2= 3 dan u3 + u5 =90 maka jumlah 4 suku pertamanya adalah
Ditanyakan oleh: USER4854
87 Dilihat
87 Jawaban
Jawaban (87)
Un = ar^(n-1)
U2 = ar = 3
a = 3/r .........(1)
U3 + U5 = ar² + ar^4 = 90
ar²(1 + r²) = 90
masukan (1)
(3/r)r²(1 + r²) = 90
3r(1 + r²) = 90
r = 3, masukan pd salahsatu
a = 3/3= 1
Sn = a(r^n - 1)/(r - 1)
S4 = 1(3^4 - 1)/(3 - 1) = 40
U2 = ar = 3
a = 3/r .........(1)
U3 + U5 = ar² + ar^4 = 90
ar²(1 + r²) = 90
masukan (1)
(3/r)r²(1 + r²) = 90
3r(1 + r²) = 90
r = 3, masukan pd salahsatu
a = 3/3= 1
Sn = a(r^n - 1)/(r - 1)
S4 = 1(3^4 - 1)/(3 - 1) = 40