Bài 1: Tìm x a) 25. ( 3x - 1/2 ) ² = 16 b) 3. ( 3x - 1/2 ) ³ + 1/9 - 0 ( nhanh giúp mik với ạ mik đang cần gấp )

Bài `1:`

`a) 25 . ( 3x - 1/2 )^2 = 16`

`⇔ ( 3x - 1/2 )^2 = 16/25`

`⇔` \(\left[ \begin{array}{l}3x-\frac{1}{2}=\frac{4}{5}\\3x-\frac{1}{2}=\frac{-4}{5}\end{array} \right.\) 

`⇔` \(\left[ \begin{array}{l}3x=\frac{1}{2}+\frac{4}{5}\\3x=\frac{1}{2}+\frac{-4}{5}\end{array} \right.\) 

`⇔` \(\left[ \begin{array}{l}3x=\frac{13}{10}\\3x=\frac{-3}{10}\end{array} \right.\) 

`⇔` \(\left[ \begin{array}{l}x=\frac{13}{30}\\x=\frac{-1}{10}\end{array} \right.\) 

Vậy `x` ∈ `{ 13/30 ; -1/10 }`

`b) 3 . ( 3x - 1/2 )^3 + 1/9 = 0`

`⇔ 3 . ( 3x - 1/2 )^3 = -1/9`

`⇔ ( 3x - 1/2 )^3 = -1/9 : 3`

`⇔ ( 3x - 1/2 )^3 = -1/27`

`⇒ 3x - 1/2 = -1/3`

`⇒ 3x = -1/3 + 1/2`

`⇒ 3x = 1/6`

`⇒ x = 1/6 : 3`

`⇒ x = 1/18`

Vậy `x = 1/18`

`#phamthanh`