the first term a = - 0.25
the common ratio R = - 4
Find the general term
答案係 ( - 1 )^n 4^n-2
我唔明白點解無啦啦有( - 1 )^n 走左出黎><"
解釋時請詳細點及show your steps pls~
幾易既Maths question: Geometric Sequences ( 5點分 )
2007-04-17 8:23 pm
回答 (1)
2007-04-17 10:47 pm
✔ 最佳答案
the first term a = - 0.25the common ratio R = - 4
The general term
=aR^(n-1)
=(-0.25)(-4)^(n-1)
=(-1/4)(-4)^(n-1)
=(-1)(1/4)(-1)^(n-1)[(4)^(n-1)]
=(-1)^n 4^n-2
因為(-4)^(n-1) 代表 (-1)^(n-1) 乘以 (4)^(n-1)
(-1)^(n-1) 再乘以 -1 就得到 ( - 1 )^n
收錄日期: 2021-04-13 00:22:18
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