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Giải thích các bước giải:

`c) (11x)/(2x - 3 ) - (x - 18)/(3 - 2x)`

`= (11x)/(2x - 3) + ( x - 18)/(2x - 3 )`

`= ( 11x - x + 18)/( 2x - 3 )`

`= (10x + 18)/(2x - 3)`

`-----`

`d) (x^2 - 4)/(x^2 - x) : ( x^2 + 2x )/(x - 1 )`

`= ( ( x - 2 )(x + 2 ) )/(x ( x - 1 ) . ( x - 1 )/(x ( x + 2 )`

`= ( x - 2 )/(x^2)`

`-----`

`2)`

`a) (3xy)/(9y^2)`

`= ( 3 : 9 )x(y : y^2)`

`= 1/3xy^(-1)`

`= x/(3y)`

`-----`

`b) (45x ( 3 - x))/(15x ( x - 3)^3 )`

`= ( -45x ( x - 3 ))/( 15x ( x - 3 )^3 )`

`= (-3)/(x - 3)^2`

`-----`

`c) ( 7x^2 - 7x^3)/(x^3 - 3x^2 + 3x - 1 )`

`= ( 7x^2 ( 1 - x ) )/( ( x - 1)^3 )`

`= ( -7x^2 ( x - 1 ) )/( ( x - 1 )^3 )`

`= (-7x^2)/( ( x - 1 )^2 )`

`----`

`3)`

`a) 5x - 7 = 0`

`5x = 7`

`x = 7/5`

Vậy, `x = 7/5`

`-----`

`b) 7 - 3 ( x - 2 ) = -4x - 1`

`7 - 3x + 6 + 4x + 1 = 0`

`x = -1 - 6 - 7`

`x = -14`

Vậy, `x = -14`

`-----`

`c) (3x)/4 - (1 - 3x)/(10) = 1 + (4x + 7)/5`

`(15x)/20 - ( 2 ( 1 - 3x))/20 = 20/20 + ( 4 ( 4x + 7))/20`

`( 15x - 2 + 6x )/20 = ( 20 + 16x + 28 )/20`

`15x - 2 + 6x = 20 + 16x + 28`

`21x - 2 = 16x + 48`

`21x - 16x = 48 + 2`

`5x = 50`

`x = 10`

Vậy, `x = 10`

`#tm`