Sn=n/2(2a+2(n-1)=165
n(a+(n-1)=165.
n²+n(a-1)=165........(1)
suku tengah (n+1)/2
Un+1/2=
a+2((n+1)/2-1)=15
a+n-1=15
a=16-n......(2)
(1) (2)
n²+n(16-n -1)=165......
.
n²-n²+15n=165......
n=165/15=13
dr(1)
a=16-13=3
u5= 3+4*2=11
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Sn=n/2(2a+2(n-1)=165
n(a+(n-1)=165.
n²+n(a-1)=165........(1)
suku tengah (n+1)/2
Un+1/2=
a+2((n+1)/2-1)=15
a+n-1=15
a=16-n......(2)
(1) (2)
n²+n(16-n -1)=165......
.
n²-n²+15n=165......
n=165/15=13
dr(1)
a=16-13=3
u5= 3+4*2=11