Đáp án:
Bài 2:
a,`27 .3^{x+1}= 243`
`3^{x}.3= 243:27`
`3^{x}.3= 9`
`3^{x} =9:3`
`3^{x} =3`
`3^x =3^1`
`⇒x = 1`
Vậy `x = 1`
b, `49 . 7^x = 7^5`
`49 . 7^x = 16807`
`7^x = 16807 : 49`
`7^x = 343`
`7^x = 7^3`
`⇒ x = 3`
Vậy `x = 3`
c, `(x + 1)^2 = 36`
`⇒(x + 1)^x = 6^2` hoặc `(x + 1)^x = (-6)^2`
`⇒ x + 1 = 6` hoặc `x + 1 = (-6)`
`x = 6 - 1` `x = (-6) - 1`
`x = 5` `x = -7`
Vậy `x ∈{ 5 ; -7}`
d, `(2x - 1)^5 = 243`
`(2x - 1)^5 = 3^5`
`⇒ 2x - 1 = 3`
`2x = 3 + 1`
`2x = 4`
`x = 4 : 2`
`x = 2`
Vậy `x = 2`
