`\text{a) +) Nếu x ≥ -2}`
`\text{Thì x+2 ≥ 0}`
`\text{⇒ |x+2|= x+2}`
`\text{Khi đó:}`
`\text{A=4(2x-1)-|x+2|}`
`\text{⇒ A =8x - 4 -x -2}`
`\text{⇒A =7x -6}`
`\text{+) Nếu x < -2}`
`\text{thì x+2<0 }`
`\text{⇒|x+2| = -x-2}`
`\text{Khi đó:}`
`\text{A = 4(2x-1)-|x+2|}`
`\text{⇒ A = 8x -4 -(-x -2)}`
`\text{⇒A = 8x -4+ x + 2}`
`\text{⇒A = 9x -2}`
`\text{b) Ta có:}`
`\text{A = 4(2x -1)-|x+2| =}` `1/2`
`\text{+) Nếu x ≥ -2:}`
`\text{⇒4(2x-1)-|x+2| = 7x -6=}` `1/2`
`\text{⇒7x = }` `13/2`
`\text{⇒ x}` `13/14` `\text{TM vì x ≥ -2}`
`\text{+) Nếu x<2:}`
`\text{⇒4(2x-1) - |x+2|=9x -2 =}` `1/2`
`\text{9x = }` `5/2`
`\text{x = }` `5/18` `\text{Loại vì x<2 }`
`\text{Vậy x =}` `13/14` `\text{thì A =}` `1/2`
