easy maths F.1( 20points)

1)3^(n - m)= 3^n / 3^m= 729 / 81= 9

Alternative :

3^4 = 81 , m = 4
3^6 = 729 , n = 6

3^(n - m)
= 3^(6 - 4)
= 3^2
= 9

2)1 / a^2(m-n)= a ^ - 2(m - n)= a ^ 2(n - m)= [a ^ (n - m)]^2= (a^n / a^m)^2= (16/64)^2= 1/16

Alternative :

Let a be 4 ,

4^3 = 64 , m = 3
4^2 = 16 , n = 2

1 / a^2(m-n)

= 1 / 4^2(3-2)

= 1 / 4^2

= 1/16






2011-01-24 18:33:27 補充：
or

1)

3^4 = 81 , m = 4
3^6 = 729 , n = 6

3^n - m

= 729 - 4

= 725

2011-01-24 23:40:41 補充：
指數定律 :

x^a * x^b = x^(a+b)
x^a / x^b = x^(a-b)

2011-01-24 23:52:12 補充：
1 / x^n = x ^ (- n)

2011-01-24 23:54:18 補充：
x^(ab) = (x^a)^b = (x^b)^a

我幫你啦!e d數之前做過.
如果我冇計錯:P
首先...3^m=81 and 3^n=729
3^m=81.好明顯m係4.
之後3^n=729.都好明顯n係6:)
之後3^n-m,咪姐係3^6-4.姐係9:>

另外...a^m=64 and a^n=16
a^2(m-n)... 你要明.64除16就等於a^m-n.
姐係a=4.m=3.n=2.
如果我冇計錯.應該係16.
希望我冇計錯:S

因為你聽日要交功課.所以我冇時間再check多幾次.
希望我冇計錯.因為都係幾耐之前ge數:P唔多記得.
希望可以幫到你:D

2011-01-24 18:32:55 補充：
第二題打少左個1 over.sor:P

3^n-m = 3^(n-m)
or = 3^n -m ?