Question

hitunglah 10 suku dari deret:b.60+55+50

Answer 1

60 + 55 + 50 + ...
a = U1 = 60
b = U2 - U1 = 55 - 60 = -5

Sn = n/2 (2a + (n - 1)b)
S10 = 10/2 (2.60 + (10 -1)-5)
S10 = 5 (120 + (-45))
S10 = 5 (120 - 45)
S10 = 5 x 75
S10 = 375

Answer 2

60+55+50+.....+U10 = S10
.
S10 = ..... ?
a = 60
b = -5
.
Rumum :
Un = a+(n-1)b
U10 = 60 + 9.(-5)
U10 = 60 -45
U10 = 15
.
Sn = (n/2)(a+un)
S10 = 5(60+15)
S10 = 5.75
S10 = 375 ✔

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