Môn Toán Lớp 7: |x – 1| = 2x – 5 ||x + 5 | – 4 | = 3

| x – 1 | = 2x – 5

+) TH1 : x – 1 >= 0 hay x >= 1 thì | x – 1 | = 2x – 5 => x – 1 = 2x – 5

=> x – 2x – 1 + 5 = 0

=> – x + 4 = 0

=> – x = -4

=> x = 4 ( tm )

+) TH2 : x – 1 < 0 hay x < 1 thì | x – 1 | = 2x – 5 => 1 – x = 2x – 5

=> – x – 2x + 1 + 5 = 0

=> – 3x + 6 = 0

=> – 3x = -6

=> x = -6 : ( – 3 )

=> x = 2 ( loại )

Vậy x = 4

||x + 5 | – 4 | = 3

=> {(| x + 5 | – 4 = – 3),(| x + 5 | – 4 = 3):}

=> {(| x + 5 | = 1),(| x + 5 | = 7):} => {({(x+5=-1),(x+5=1):}),({(x+5=-7),(x+5=7):})}

=> {({(x=-6),(x=-4):}),({(x=-12),(x=2):}):}

Vậy x in { -6 ; -4 ; -12 ; 2 }