Toán Lớp 7: $\frac{ $3^{x}$}{81}$ bằng 27
$\frac{$4^{x}$ }{16}$ bằng 64
$\frac{64}{ $(-2)^{x}$ }$ bằng -32
hộ em vote 5 sao
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Toán Lớp 7: $\frac{ $3^{x}$}{81}$ bằng 27
$\frac{$4^{x}$ }{16}$ bằng 64
$\frac{64}{ $(-2)^{x}$ }$ bằng -32
hộ em vote 5 sao
Comments ( 2 )
(3^x)/81=27
=>3^x=81.27
=>3^x=3^4 . 3^3
=>3^x=3^(4+3)
=>3^x=3^7
=>x=7
Vậy x=7
b)
4^x/16=64
=>4^x=16.64
=>4^x=4^2 . 4^3
=>4^x=4^(2+3)
=>4^x=4^5
=>x=5
Vậy x=5
64/(-2)^x=-32
=>64/(-2)^x=(-2)^5
=>(-2)^x . (-2)^5=64
=>(-2)^(x+5)=2^6
=>(-2)^(x+5)=(-2)^6
=>x+5=6
=>x=6-5
=>x=1
Vậy x=1