Jawabanmu

2014-05-19T10:29:42+07:00
A= 6

U₅ = a+(n-1)b
22 = 6+4b
22-6 = 4b
16   = 4b
4     = b


S₄₀ = n/2 [2a+(n-1)b)
      = 40/2[2.6+39.4)
      = 20[12+156]
      = 20[168]
      = 3360

maaf kalau salah:)
2014-05-19T11:08:46+07:00
U5=a+4b=22
6+4b=22
4b=16
b=4
S20=n/2(2a+19b)
10(2.6+19.4)
10(12+76)
10(88)
S20=880