Penjelasan dengan langkah-langkah:
u1 + u2 = 4
s(2) = 4
u(1) + u(2) + u(3) + u(4)
= 40
s(4) = 40
s(2) = a(r² - 1)/ r - 1
s(4) = a(r⁴ - 1)/r-1
40 = a(r² + 1)(r² - 1)/r - 1
= (r² - 1)(s(2))
= (r² + 1)(4)
= r² + 1 = 10
r² = 9
r = √9 = 3
u(1) + u(2) = 4
a + ar = 4
a + 3a = 4
4a = 4
a = 1
s(5) = a(r² -1)/r - 1
= (1)(3^5 -1)/3 - 1
= 3^5 - 1/2
= 242 - 1/2
= 242 ÷ 2
= 121
Penjelasan dengan langkah-langkah:
[tex]u(1) + u(2) = 4 \\ s(2) = 4 \\ \\ u(1) + u(2) + u(3) + u(4) = 40 \\ s(4) = 40 \\ \\ s(2) = \frac{a( {r}^{2} - 1 )}{r - 1} \\ \\s(4) = \frac{a( {r}^{4} - 1) }{r - 1} \\ 40 = \frac{a( {r}^{2} + 1)( {r}^{2} - 1) }{r - 1} \\ 40 = ({r}^{2} + 1)(s(2)) \\ 40 = ( {r}^{2} + 1)(4) \\ {r}^{2} + 1 = 10 \\ {r}^{2} = 9 \\ r = \sqrt{9} \\ r = 3 \\ \\ u(1) + u(2) = 4 \\ a + ar = 4 \\ a + 3a = 4 \\ 4a = 4 \\ a = 1 \\ \\ s(5) = \frac{a( {r}^{5} - 1) }{r - 1} \\ s(5) = \frac{(1)( {3}^{5} - 1) }{3 - 1} \\ s(5) = \frac{ {3}^{5} - 1 }{2} \\ s(5) = \frac{243 - 1}{2} \\ s(5) = \frac{242}{2} \\ s(5) = 121 [/tex]
