toán 6

T

t.hlin

1,
2^x .4 = 128 nên 2^x = 32
ta có 32 =2^5 nên 2^5= 2^x suy ra x=5
2
ta có 1^1 =1 ; 1^2 =1 .............. 1^n =1 nên x^15 = x suy ra x=+1 ,-1,0
3
( 2x+1)^3 =125 => 2x+1 = 5 => x=2
 
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T

tayhd20022001


a ) $2^x$ . 4 = 128
\Rightarrow $2^x$=128:4
\Rightarrow $2^x$=32
\Rightarrow $2^x$=$2^5$
\Rightarrow x=5
b ) $x^{15}$ = x
Ta có :3TH
\Rightarrow TH1: x=1
\Rightarrow TH2: x=0
\Rightarrow TH3: x=(-1)
c ) $(2x + 1)^3$ = 125
\Rightarrow $(2x + 1)^3$ = $5^3$
\Rightarrow 2x + 1= 5
\Rightarrow 2x =5-1
\Rightarrow 2x =4
\Rightarrow x=4:2
\Rightarrow x=2
 
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