Đáp án+Giải thích các bước giải:
BT9:
a,$125^{5}$:$25^{3}$ =$(5³)^{5}$:$(5²)^{3}$=$5^{15}$:$5^{6}$=$5^{9}$
b,$27^{6}$:$9^{3}$=$(3³)^{6}$:$(3²)^{3}$=$3^{18}$:$3^{6}$=$3^{12}$
c,$4^{20}$:$2^{15}$=$(2²)^{20}$:$2^{15}$=$2^{40}$:$2^{15}$=$2^{25}$
d,$24^{n}$:$2^{2n}$=$(4×6)^{n}$:$2^{2n}$=$4^{n}$×$6^{n}$:$2^{2n}$ =$2^{2n}$×$6^{n}$:$2^{2n}$=$6^{n}$
e,$64^{4}$×$16^{5}$:$4^{20}$=$2^{24}$×$2^{20}$:$2^{40}$=$2^{4}$
g,$32^{4}$:$8^{6}$=$2^{20}$:$2^{18}$=$2^{2}$
BT10:
a,$2^{x}$×4=128 b,(2x-1)³=125 c,$2^{x}$-26=6
$2^{x}$ =128:4 (2x-1)³=5³ $2^{x}$ =6+26
$2^{x}$ =32 ⇒2x+1=5 $2^{x}$ =32
$2^{x}$ =$2^{5}$ ⇒2x =6 $2^{x}$ =$2^{5}$
⇒x=5 ⇒x=3 ⇒x=5
Vậy x=5 Vậy x=3 Vạy x=5
d,64×$4^{x}$=$4^{5}$ e,27×$3^{x}$=243 g,49×$7^{x}$=2401
$4^{3}$×$4^{x}$=$4^{5}$ $3^{x}$=243:27 $7^{x}$=2401:49
$4^{x}$=$4^{5}$: $4^{3}$ $3^{x}$=9 $7^{x}$=49
$4^{x}$=$4^{2}$ $3^{x}$=$3^{2}$ $7^{x}$=$7^{2}$
⇒x=2 ⇒x=2 ⇒x=2
Vậy x=2 Vậy x=2 Vậy x=2
h,$3^{x}$=81 k,$3^{4}$×$3^{x}$=$3^{7}$ n,$3^{x}$+25=26.2²+2.$3^{0}$
$3^{x}$=$3^{4}$ $3^{x}$=$3^{7}$:$3^{4}$ $3^{x}$+25=26.4+2.1
⇒x=4 $3^{x}$=3³ $3^{x}$+25=106
Vậy x=4 ⇒x=3 $3^{x}$ =106-25
Vậy x=3 $3^{x}$ =81
$3^{x}$ =$3^{4}$
⇒x=4
Vậy x=4
