Đáp án:
Giải thích các bước giải:
` Bài 15 : `
`a, | x+2 | = 5`
`<=> $\left \{ {{x+2=5} \atop {x+2=-5}} \right.$`
`<=> $\left \{ {{x=3} \atop {x=-7}} \right.$ `
`Vậy $\left \{ {{x=3} \atop {x=-7}} \right.$ `
` b, | x+3 | =15`
`<=> $\left \{ {{x+3=15} \atop {x+3=-15}} \right.$ `
`<=> $\left \{ {{x=5} \atop {x=-18}} \right.$ `
` Vậy $\left \{ {{x=5} \atop {x=-18}} \right.$ `
`c, |x – 7| + 13 = 25`
`<=> |x – 7| = 12`
`<=> $\left \{ {{x-7=12} \atop {x-7=-12}} \right.$`
`<=> $\left \{ {{x=19} \atop {x=-5}} \right.$ `
` Vậy $\left \{ {{x=19} \atop {x=-5}} \right.$ `
`d) |x – 3| - 16 = - 4`
` |x – 3| = 12 `
`<=> $\left \{ {{x-3=12} \atop {x-3=-12}} \right.$ `
`<=> $\left \{ {{x=15} \atop {x=-9}} \right.$ `
` Vậy $\left \{ {{x=15} \atop {x=-9}} \right.$ `
`e, 3 + x = 2`
`<=> x=2-3`
`<=> x = -1 `
`Vậy x=-1`
