Geometric series help!?
Find the sum of the geometric series of 5+y+(y^2/3)+(y^3/9)+...
I know the a=5, and the r = y/3, but the sum isn t 5/(1-y/3). Please help
回答 (1)
It's not a geometric series:
y/5 =/= (y^2/3)/y = y/3
you can split it up:
2 + (3 + y + y^2/3 + y^3/9 + ..)
and then the bit in brackets is geometric, the sum is then:
2 + 3/(1-(y/3))
= 2 + 9/(3-y)
= (15 - 2y)/(3 - y)
收錄日期: 2021-04-21 17:59:53
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