中4 M1數2條

2010-02-09 4:06 am
要步驟+答案thx~

1.若2(3^2n)+3^2n+1=45 , 求n的值

2.若81^2x=27^y , 求x:y
更新1:

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回答 (1)

2010-02-09 4:11 am
✔ 最佳答案
1)2(3^2n)+3^2n+1=45
2(3^2n) + 3(3^2n) = 45
5(3^2n) = 45
3^2n = 9
3^2n = 3^2
2n = 2
n = 1
2)81^2x=27^y
(3^4)^2x = (3^3)^y
3^8x = 3^3y
8x = 3y
x/y = 3/8
3 : 8


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