中三數學 急! 10點

[(3^n)-3^(n-1)]/{2[3^(n-1)]}
= [3^(n-1)][2*3-1]/[2*3^(n-1)]
= [2*3-1]/2
= 5/2

[2(3^n)-3^(n-1) / [2*3^(n-1)]

= 3^(n-1)*(2*3-1) / [2*3^(n-1)]

= (2*3-1) / 2

= 5/2

As follow AS~~

圖片參考：http://www.photo-host.org/img/835891screenhunter_02_nov._01_11.14.gif

[2(3^n)-3^(n-1)]/2[3^(n-1)]
=[3^(n-1)][2(3)-1]/2[3^(n-1)]...........抽個3^(n-1)出泥,同下面約左佢0.0
=(6-1)/2
=5/2

同我張UT pass paper ge 問題一樣

2(3^n)-3^n-1 / 2(3^n-1)
=3^n-1(2*3-1) / 2(3^n-1)
=6-1/2
=5/2

[ 2(3^n) - 3^(n-1) ] / [ 2 * 3^(n-1) ]
= 3^(n-1) * [ 2*3 - 1 ] / [ 2 * 3^(n-1) ]
= [ 2*3 - 1 ] / 2
= 5/2