deret geometri u1+u6= 244 ,, u3×u4=243,,s4=...?

Un = ar^(n-1)

maka
U1+U6=244
a + ar^5 = 244
ar^5 = 244-a

U3 x U4 = 243
ar² x ar³ = 243
a(ar^5) = 243
a(244-a) = 243
244a - a²=243
a²-244a+243=0
(a-243)(a-1)
a=243 atau a=1
pilih a=1

a+ar^5 = 244
1+(1)r^5=244
r^5 = 244-1
r^5 = 243
r= 3

jadi. S4
S4 = a(r⁴-1) / r-1
=1(3⁴-1)/3-1
=(81-1)/2
=80/2
=40