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Mr-Brian 2006-10-26 22:11

Form3 maths急問,聽日test牙!!!!岩哂10000好友元

question1

a )Expand (x+x^-1)^2
  b )given that x   + x^-1   = 5 ,determine x^2 + x^-2


question2

  If x+ 1/x = 5, find x^2/x^4+x^2+1

question3

  2^2x+1 +   2^2x-1   =   203

find x

question4

  2^x+3   +2^x   = 9/16

find x



連step!!!唔好move住!!過左聽日先move唔該

黑魔導眾 2006-10-26 22:13
Type English only ok ?

Mr-Brian 2006-10-26 22:13
引用第1樓黑魔導眾2006-10-26 22:13發表的“”:
Type English only ok ? [表情] [表情] [表情] [表情] [表情] [表情]

唔識點打D index出黎

英俊 2006-10-26 22:15
2既2x+1次方+2既2x-1次方=203

2既2x=4x?
what is 1次方?

Mr-Brian 2006-10-26 22:15
引用第3樓handsome 仔2006-10-26 22:15發表的“”:
2既2x+1次方+2既2x-1次方=203
2既2x=4x?
what is 1次方?

即係個Index係 2x+1

Mr-Brian 2006-10-26 22:16
Mach仔幫我計計啦

英俊 2006-10-26 22:17
i don't know what you say
all use 數字ok?

Mr-Brian 2006-10-26 22:18
引用第6樓handsome 仔2006-10-26 22:17發表的“”:
i don't know what you say
all use 數字ok?

我唔識打d index出黎牙 點打?

英俊 2006-10-26 22:18
ps:
2的2次方=2^2
try to use

麥精 2006-10-26 22:18
引用第5樓abbrian20052006-10-26 22:16發表的“”:
Mach仔幫我計計啦 [表情]

我啱啱先肥左

英俊 2006-10-26 22:19
i am f.3 and i think i learnt

英俊 2006-10-26 22:20
question3

2既2x+1次方+2既2x-1次方=203

find x


2^2x+1   + 2^2x-1=203?

Mr-Brian 2006-10-26 22:22
引用第11樓handsome 仔2006-10-26 22:20發表的“”:
question3
2既2x+1次方+2既2x-1次方=203
find x
.......

55

鮮吊甬仔 2006-10-26 22:23
question4

2既x+3次方+2既x次方 = 9/16
2^x * 2^3 +2^x= 9/16
2^x*8+2^x= 9/16
2^x(8+1)=9/16
2^x=1/16
2^x=2^-4

SO, X=-4

SuNFoReVeR 2006-10-26 22:24
question4

2既x+3次方+2既x次方 = 9/16

find x


2^(x+3)   +   2^x
=(2^x)(2^3) + 2^x
=(抽CONNON FACTOR)2^x((2^3)+1)
=2^x(9)



2^x(9)=9/16
2^x=1/16
2^x=2^-4

所以 x=-4

英俊 2006-10-26 22:24
impossible 203

麥精 2006-10-26 22:24
真係唔識

Mr-Brian 2006-10-26 22:25
引用第13樓Skyline2006-10-26 22:23發表的“”:
question4
2既x+3次方+2既x次方 = 9/16
2^x * 2^3 +2^x= 9/16
2^x*8+2^x= 9/16
.......

THX 2500聽日過

Mr-Brian 2006-10-26 22:25
引用第16樓mach仔2006-10-26 22:24發表的“”:
真係唔識 [表情]

我d數都係f.3,我平時maths都ok,but真係唔識

麥精 2006-10-26 22:30
x^2/x^4+x^2+1

係 x^2/x^4+x^2 +1?

麥精 2006-10-26 22:33
Q3

2^4X = 203

冇可能喎...

銘〝 2006-10-26 22:33
引用第20樓mach仔2006-10-26 22:33發表的“”:
Q3
2^4X = 203
冇可能喎...

係囉...計唔到架喎

SuNFoReVeR 2006-10-26 22:34
a )Expand (x+x^-1)^2
b )given that x   + x^-1   = 5 ,determine x^2 + x^-2


A) =x^2+2(x)(x^-1)+x^-2
=x^2+(x^-2)+2

b)x+x^-1=5
TAKE SQUARE BOTH SIDE
x^2+(x^-2)+2=25
x^2+(x^-2)=25-2=23

英俊 2006-10-26 22:35
引用第20樓mach仔2006-10-26 22:33發表的“”:
Q3
2^4X = 203
冇可能喎...

引用第15樓handsome 仔2006-10-26 22:24發表的“”:
impossible 203


Mr-Brian 2006-10-26 22:36
引用第21樓calvin022006-10-26 22:33發表的“”:
係囉...計唔到架喎

個答案係3/2

豬脾 2006-10-26 22:36
q1
x^2+2+x-2
b.(x+x^-1)^2=x^2+2+x^-2
25=x^2+2+x^-2
x^2+x^-2=23

銘〝 2006-10-26 22:36
a )Expand (x+x^-1)^2
=(x+a/x)^2
=x^2+2+1/x^2
b.(x+x^-1)^2=x^2+2+x^-2
25=x^2+2+x^-2
x^2+x^-2=23

Mr-Brian 2006-10-26 22:37
引用第22樓SuN FoReVeR2006-10-26 22:34發表的“”:
a )Expand (x+x^-1)^2
b )given that x   + x^-1   = 5 ,determine x^2 + x^-2
A) =x^2+2(x)(x^-1)+x^-2
=x^2+(x^-2)+2
b)x+x^-1=5
TAKE SQUARE BOTH SIDE
x^2+(x^-2)+2=25
x^2+(x^-2)=25-2=23
.......

點黎架????

麥精 2006-10-26 22:38
引用第24樓abbrian20052006-10-26 22:36發表的“”:
個答案係3/2 [表情]


Mr-Brian 2006-10-26 22:39
引用第26樓calvin022006-10-26 22:36發表的“”:
a )Expand (x+x^-1)^2
=(x+a/x)^2
=x^2+2+1/x^2
b.(x+x^-1)^2=x^2+2+x^-2
25=x^2+2+x^-2
.......

邊度有個a出黎?

SuNFoReVeR 2006-10-26 22:39
引用第27樓abbrian20052006-10-26 22:37發表的“”:
點黎架????

2(x)(x^-1)
=2(x)(1/X)=2


BY IDENTITY (a+b)^2=a^2+2ab+b^2

唔知中三學左未

英俊 2006-10-26 22:40
引用第30樓SuN FoReVeR2006-10-26 22:39發表的“”:
2(x)(x^-1)
=2(x)(1/X)=2
.......

taught

Mr-Brian 2006-10-26 22:41
引用第30樓SuN FoReVeR2006-10-26 22:39發表的“”:
2(x)(x^-1)
=2(x)(1/X)=2
.......

係wor

SuNFoReVeR 2006-10-26 22:41
引用第31樓handsome 仔2006-10-26 22:40發表的“”:
taught

i see.....

SuNFoReVeR 2006-10-26 22:42
引用第32樓abbrian20052006-10-26 22:41發表的“”:
係wor [表情] [表情]

第四題都係差唔多計法...不過就要抽個x^2出黎

Mr-Brian 2006-10-26 22:45
仲有2,3未計

SuNFoReVeR 2006-10-26 22:47
第3題如果答案係3/2既話....

咁應該係20唔係203

Mr-Brian 2006-10-26 22:48
引用第36樓SuN FoReVeR2006-10-26 22:47發表的“”:
第3題如果答案係3/2既話....
咁應該係20唔係203 [表情]

張野係咁寫

亨利仔 2006-10-26 22:51
哈哈...一見到呢d就會頭暈

SuNFoReVeR 2006-10-26 22:53
引用第37樓abbrian20052006-10-26 22:48發表的“”:
張野係咁寫 [表情]

可能打錯

If x+ 1/x = 5, find x^2/x^4+x^2+1


x+ 1/x = 5又係take square就會得出

x^2+x^-2+2=25
x^2+^-2=23

x^2/x^4+x^2+1
=(分母抽x^2) x^2/((x^2)(x^2+1+x^-2)
=(cancel x^2)1/((x^2)(x^2+x^-2+1)
=1/(23+1)
=1/24
???

英俊 2006-10-26 22:53
question 2 answered?

CKL 2006-10-26 22:54
第3題9成打錯啦
如果係203個ans係1.916333979.....

豬脾 2006-10-26 23:05
引用第41樓CKL2006-10-26 22:54發表的“”:
第3題9成打錯啦
如果係203個ans係1.916333979.....

log
2^x X 2+2^x/2=203
2^x(2+1/2)=203
2^x=203/(2+1/2)
xlog2=log203/(2+1/2)
x=3.171703911

豬脾 2006-10-26 23:19
其他個d都係咁log就得啦
嗚謝幕後教路既kai王

亨利仔 2006-10-26 23:25
引用第43樓卡卡....2006-10-26 23:19發表的“”:
其他個d都係咁log就得啦
嗚謝幕後教路既kai王 [表情]

kai王d數真係好勁...

小學果陣已經係咁

jov 2006-10-26 23:27
我黎遲左呀?

BBF 2006-10-26 23:37
我都有諗log先
不過見你地d方法咁直接喎

數學有時奇妙在可以用唔同方法計到
殊途同歸
答案始終一天找到了

CKL 2006-10-26 23:40
引用第42樓卡卡....2006-10-26 23:05發表的“”:
log [表情]
2^x X 2+2^x/2=203
2^x(2+1/2)=203
2^x=203/(2+1/2)
.......

係bo
禁錯機
我頭先都用log
不過F.3教左未?

BBF 2006-10-26 23:50
F.3應該教左
log 10
log 其他就可能未

BBF 2006-10-26 23:59
question2

If x+ 1/x = 5, find x^2/x^4+x^2+1

係咪 x^2/(x^4+x^2+1)?


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