一條好tricky既數

有兩個方法可以做這題.

方法一:
4^x = 10^4
4^x = 10000
xlog4 = log10000
x = log10000 / log4
x = 6.64385619

將 x = 6.64385619 代入 8^x,
8^6.64385619
= 1000000
= 10^6

方法二:
4^x = 10^4
(2^2)^x = 10^4
(2)^(2x) = 10^4
(2^x)^2 = 10^4
2^x = 10^2

8^x
= (2^3)^x
= (2)^(3x)
= (2^x)^3
= (10^2)^3 <-- 將(2^x = 10^2)代入
= 10^6

如果你未學log, 你用方法二比較好.
有錯請指正!

4^x=10^4
4^x=10000
xlog4=log10000
x=log10000/log4
x=6.64385619

sub. x=6.64385619 into 8^x=?
that is 8^6.64385619
=1000000
=10^6