Bài 2: (2,0 điểm) Tìm x, biết: a) $\frac{1}{3}$x + $\frac{2}{5}$(x - 1) = 0 b) (2x + 1)² = $\frac{36}{25}$ c) $\frac{1}{2}$x + $\sqrt{0,04}$ = $\sqrt{1,96}$ d) ||2x + 1| + $\frac{1}{2}$| = $\frac{4}{5}$

`a) 1/3 x + 2/5 (x - 1) = 0`

`=> 1/3 x + 2/5 x - 2/5 = 0`

`=> 11/25 x = 2/5`

`=> x = 2/5 : 11/25`

`=> x = 6/11`

Vậy `x = 6/11`

`b) (2x + 1)^2 = 36/25`

`=> (2x + 1)^2 = (6/5)^2`

`=> 2x + 1 = 6/5` hoặc `2x + 1 = -6/5`

`=> 2x = 1/5` hoặc `2x = -11/5`

`=> x = 1/10` hoặc `x = -11/10`

Vậy `x = 1/10` hoặc `x = -11/10`

`c) 1/2x + sqrt(0,04) = sqrt(1,96)`

`=> 1/2x = sqrt(1,96) - sqrt(0,04)`

`=> 1/2x = 6/5`

`=> x = 6/5 - 1/2`

`=> x = 7/10`

Vậy `x = 7/10`

`d) ||2x - 1| + 1/2| = 4/5`

`=> |2x - 1| = 4/5 - 1/2`

`=> |2x - 1| = 3/10`

`=> 2x - 1 = 3/10` hoặc `2x - 1 = -3/10`

`=> 2x = 13/10` hoặc `2x = 7/10`

`=> x = 13/20` hoặc `x = 7/20`

Vậy `x = 13/20 ; x = 7/20`