如果
x,100,y is geometric sequence,
find the value of :log x+log y
Maths教我呀~中五sequences~20分題目~快快快~
2007-09-24 3:24 am
回答 (2)
2007-09-24 3:43 am
✔ 最佳答案
Let a be the first term, r be the common ratio(設a是首項,r是公比)a=x---------(1)
ar=100-----(2)
ar2次=y----(3)
so,r=100/x=y/100
xy=10000
log xy=4
log x+log y=4
試下代入1d數
e.g x=1 y=10000
x=10 y=1000
x=4 y=2500
點計都係4
如果係mc可以試下咁做
2007-09-25 10:15 pm
Let r be the common ratio
log x + log y = log xy
= log (x)(xr^2)
= log (xr)^2
= log 100^2 , xr=100
= 4
log x + log y = log xy
= log (x)(xr^2)
= log (xr)^2
= log 100^2 , xr=100
= 4
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