Đáp án:
Giải thích các bước giải:
`3)`$\frac{81}{3^{x+1}}$ `=3`
`⇔3.3^{x+1}=81`
`⇔3^{x+1}=81:3`
`⇔3^{x+1}=27`
`⇔3^{x+1}=3^3`
`⇔x+1=3`
`⇔x=3-1`
`⇔x=2`
Vậy `x=2`
`6)`$\frac{625}{5^{x+1}}$`=5^2`
`⇔`$\frac{625}{5^{x+1}}$`=25`
`⇔25.5^{x+1}=625`
`⇔5^{x+1}=625:25`
`⇔5^{x+1}=25`
`⇔5^{x+1}=5^2`
`⇔x+1=2`
`⇔x=2-1`
`⇔x=1`
Vậy `x=1`
`8)`$\frac{64}{4^{x+2}}$`=4`
`⇔4.4^{x+2}=64`
`⇔4^{x+2}=64:4`
`⇔4^{x+2}=16`
`⇔4^{x+2}=4^2`
`⇔x+2=2`
`⇔x=2-2`
`⇔x=0`
Vậy `x=0`
`9)`$\frac{16}{4^{x+1}}$`=4^2`
`⇔`$\frac{16}{4^{x+1}}$`=16`
`⇔16.4^{x+1}=16`
`⇔4^{x+1}=16:16`
`⇔4^{x+1}=1`
`⇔4^{x+1}=4^0`
`⇔x+1=0`
`⇔x=0-1`
`⇔x=-1`
Vậy `x=-1`
`9)`$\frac{49}{7^{x+1}}$`=7`
`⇔7.7^{x+1}=49`
`⇔7^{x+1}=49:7`
`⇔7^{x+1}=7^1`
`⇔x+1=1`
`⇔x=1-1`
`⇔x=0`
Vậy `x=0`
