Maths教我呀~中五sequences~20分題目~快快快~

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

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