Đáp án+Giải thích các bước giải:

`{(3x + y = 3),(2x - y= 7):}`

`<=> {(5x = 10),(2x - 7 = y):}`

`<=> {(x = 2),(y = -3):}`

` Vậy  ( x ; y ) = ( 2 ; -3 )`

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`{(2x + 5y = 8),(2x - 3y = 0):}`

`<=> {(8y = 8),(2x = 3y):}`

`<=> {(y = 1),(2x = 3):}`

`<=> {(y = 1),(x = 3/2):}`

` Vậy  ( x ; y ) = ( 3/2 ; 1 )`

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`{(4x + 3y = 6),(2x + y = 4):}`

`<=> {(4x + 3y = 6),(4x + 2y = 8):}`

`<=> {(y = -2),(2x = 4 - y):}`

`<=> {(y = -2),(2x = 6):}`

`<=> {(y = -2),(x = 3):} `

` Vậy  ( x ; y ) = ( 3 ; -2 )`

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`{(2x + 3y = -2),(3x - 2y = -3):}`

`<=> {(4x + 6y = -4),(9x - 6y = -9):}`

`<=> {(13x = -13),(3x + 3 = 2y):}`

`<=> {(x = -1),(2y = 0):}`

`<=> {(x = -1),(y = 0):}`

` Vậy  ( x ; y ) = ( -1 ; 0 )`

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`{(0.3x + 0.5y = 3),(1.5x - 2y = 1.5):}`

`<=> {(3x + 5y = 30),(3x - 4y = 3):}`

`<=> {(9y = 27),( 3x = 4y + 3):}`

`<=> {(y=  3),(3x = 15):}`

`<=> {(x = 5),(y = 3):}`

` Vậy  ( x ; y ) = ( 5 ; 3 )`