Jawabanmu

2014-06-24T15:03:55+07:00
U₁+U₂ = a+ar = 24
U₁+U₂+U₃+U₄ = a+ar+ar²+ar³ = 240
ar²+ar³ = 216
a+ar = 216/r²
24 = 216/r²
r=3

a+ar = a+a.3 = 24
4a = 24
a = 6

U₅ = ar⁴ = 6.3⁴ = 486
2014-06-24T15:05:50+07:00
A+ar = 24 a+(ar)+ar^2+ar^3=240 24+r^2(a+ar)=240 24+24r^2=240. 1+r^2=10 r^2=9. r=3 a+3a=24. a=6. U=ar^4=6(3)^4 =486. jwbn: e.486