4^(x+1) - 4^(x-1) = 60
x=?
我唔記得左呢d數點計= ="
中3指~thx(好易)
2007-09-01 8:27 am
回答 (2)
2007-09-01 8:37 am
✔ 最佳答案
4^ ( x + 1 ) - 4 ^ ( x - 1 ) = 60 ( 4^x )( 4^1 ) - ( 4^x )( 4^-1 ) = 60 { 根據指數法則: ( a^m )( a^n ) = a^ ( m + n ) }
4^x ( 4 - 1 / 4 ) = 60 { 分解因式 }
4^x ( 3.75 ) = 60
4^x = 16
4^x = 4^2
x = 2
參考: My Maths Knowledge
2007-09-01 8:44 am
只要化成同一個數底便可以了, 即係兩個都變成4^x
4^(x+1) - 4^(x-1) = 60
4(4^x)-1/4(4^x)=60
15/4(4^x)=60
4^x=60÷15/4=16
x=2
4^(x+1) - 4^(x-1) = 60
4(4^x)-1/4(4^x)=60
15/4(4^x)=60
4^x=60÷15/4=16
x=2
收錄日期: 2021-04-23 00:16:59
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