f5 maths 一問(急)盡快答plz*20點=]
2009-12-01 8:25 pm
solve:
17(a)5^x+1+5^x-5^x-1=29
17(b)3^x+3-2(3^x+2)+3^x=30
17(c)2^2x-5(2^x)+4=0
17(d)4^2x-10(4x)+16=0
solve the following simultaneous equations
18(a)4^x+2y=64
16^2x-y=1
18(b)3^x+y=9^2x-y
9^3x+y=9
find the values without using calculator
19(a)-1/2 log625-log4
19(b)log32 - log64/log128
19(c)3 log 3 - log 243/log9
19(d)1.5 log 16 - 2log 2/log 36- 2 log 3
simplify
20(a)log a^4 + log b ^8/log ab^2
20(b) 4 log x^2 + 2 log x ^4/ log x^3
20(c) log 開方xy - log x 開方 y/ log 開3方xy – log (x ．開3方y)
20(d) log a^2 b – log ab/ log ab^2 –log a^2 b^2
solve
21(a)log (3x-2)+log 2 =1
21(b) log 2x +6log 2= log 96
21(c)log(3) (4x-2) – log (3) (x+1)=1
21(d) log (5) (3x+3)- log(5) (x-1) = 2log(5) 開方5
21(e) [log(3) (2x+3)]^2 – 4log(3) (2x+3)+3=0
solve the following simultaneous equations
22(a) log x + 2 log y=2
3x-2y=2
22(b) log (6x-5y)=1
log xy – log 2=1
答到幾多得幾多..答得最多果個我選佢做最佳=]
thz for your help.
回答 (2)
2009-12-02 4:01 am
✔ 最佳答案
17(a)5x+1+5x-5x-1=295(5x)+5x-1/5(5x)=29
29/5(5x)=29
5x=5
x=1
17(b)3x+3-2(3x+2)+3x=30
27(3x)-18(3x)+3x=30
10(3x)=30
3x=3
x=1
17(c)22x-5(2x)+4=0
(2x)2-5(2x)+4=0
(2x-4)(2x-1)=0
2x=4 or 2x=1
x=2 or x=0
17(d)42x-10(4x)+16=0
(4x)2-10(4x)+16=0
(4x-8)(4x-2)=0
4x=8 or 4x=2
x=3/2 or x=1/2
18(a)4x+2y=64_______________________(1)
162x-y=1____________________________(2)
Form(1),we have,
4x+2y=43
x+2y=3_____________________________(3)
Form(2),we have,
162x-y=160
2x-y=0______________________________(4)
(3)x2-(4):5y=6
y=6/5
Subst. y=6/5 into(3)
x+2(6/5)=3
x=3/5
18(b)3x+y=92x-y_________________________(1)
93x+y=9________________________________(2)
Form(1),we have,
3x+y=22(2x-y)
x+y=4x-2y
3x-3y=0____________________________(3)
Form(2),we have,
93x+y=90
3x+y=0______________________________(4)
(3)-(4):-4y=0
y=0
Subst. y=0 into(3)
3x+0=0
x=0
19(a)-1/2 log625-log4
=-log6251/2-log4
=-log25-log4
=-(log25+log4)
=-log100
=-2
圖片參考：http://h.imagehost.org/0089/ScreenHunter_01_Dec_01_19_56.gif
21(b) log 2x +6log 2= log 96
log2x+log26=log96
log2x+log64=log96
log(2x)(64)=log96
log128x=log96
128x=96
x=3/4
21(c)log3(4x-2) – log3(x+1)=1
log3(4x-2)/(x+1)=1
(4x-2)/(x+1)=3
4x-2=3x+3
x=5
21(d) log5(3x+3)- log5(x-1)=2log5√5
log5(3x+3)/(x-1)= log55
(3x+3)/(x-1)=5
3x+3=5x-5
2x=8
x=4
21(e) [log3(2x+3)]2–4log3(2x+3)+3=0
[log3(2x+3)-3][log3(2x+3)-1]=0
log3(2x+3)=3 or log3(2x+3)=1
2x+3=33 or 2x+3=3
2x=6 or 2x=0
x=3 or x=0
2009-12-01 8:37 pm
1-1=0 154564.bgj4 45
收錄日期: 2021-04-23 20:41:02
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20091201000051KK00447