Đáp án:
`x = 3 `
Giải thích các bước giải:
`e)` $3^{-1}$ . $4^{x}$ `+ 3 .` $4^{x}$ `=` `5/3` . $2^{7}$
`=>` $4^{x}$ .` (` $3^{-1}$ `+ 3 ) =` `5/3` `. 128`
`=>` $4^{x}$ . `(` `1/3` +` 3 )` `=` `640/3`
`=>` $4^{x}$ `. (` `1/3` `+` `9/3` `) =` `640/3`
`=>` $4^{x}$ . `10/3` `=` `640/3`
`=>` $4^{x}$ `=` `640/3` `:` `10/3`
`=>` $4^{x}$ `=` `640/3` . `3/10`
`=>` $4^{x}$ `= 64`
`=>` $4^{x}$ `= 4³`
`=> x = 3 `
Vậy `x = 3 `
