請幫我計以下既問題,我計左好耐都唔識....
1. If x－x^-1=1
and x^2＋x^-2 =3
find the value of x^4＋x^-4.
2. If log2= s, log3= t
log25=??
Express the following in terms of s and t.
3. If log (3y/x)=log(x+1)－logy
express y in terms of x.
急!!中4數學問題 ,(有3題)
2008-05-22 5:03 am
回答 (1)
2008-05-22 7:33 am
✔ 最佳答案
x^4＋x^-4=(x^2＋x^-2)^2-2
=3-2
=1
2
log25
=log5^2
=2log5
=2(log10-log2)
=2(1-s)
3
log (3y/x)=log(x+1)－logy
log (3y/x)=log[(x+1)/y]
3y/x=(x+1)/y
3y^2=x^2+x
y=sqrt[1/3(x^2+x)]
收錄日期: 2021-04-25 16:58:16
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20080521000051KK02611