Question 1177555
Arithmetic:
m is -25 d=-5
-15,-20,-25,-30,-35
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this is an=a1+(n-1)d=-15+(n-1)(-5)
series is 15,-20,-25,-30,-35
a5=-15+4(-5)=-35
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an=a(n-1)-5
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Sn=(n/2)(2a1+(n-1)d)
S10=5(-30+9(-5))=-375
series of -15,-20,-25,-30,-35,-40,-45,-50,-55,-60
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n=625 and r=0.2 or 1/5
625,125,25,5,1
rule is a(n)=a(n-1)*(1/5)
an=ar^(n-1)  so a10=(.2^9)=0.00032, this is also, continuing from above(1/5+(1/25)+(1/125)+(1/625)+(1/3125)), where 1/3125 is the 10th term of the sequence. Note: 1/3125 is 0.00032.
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summation is S25=(a (1-r^25)/(1-r))
625(1-.2^25/.8=781.25
This is the limit of the series, which is a/(1-r)=625/.8=781.25