Form3 maths急問,聽日test牙!!!!岩哂10000好友元 [復制鏈接]

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



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Type English only ok ?

引用第1樓黑魔導眾於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

2既2x+1次方+2既2x-1次方=203

2既2x=4x?
what is 1次方?

引用第3樓handsome 仔於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

Mach仔幫我計計啦

i don't know what you say
all use 數字ok?

引用第6樓handsome 仔於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?

ps:
2的2次方=2^2
try to use

引用第5樓abbrian2005於2006-10-26 22:16發表的“”:
Mach仔幫我計計啦 [表情]

我啱啱先肥左

i am f.3 and i think i learnt

question3

2既2x+1次方+2既2x-1次方=203

find x


2^2x+1   + 2^2x-1=203?

引用第11樓handsome 仔於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

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

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