………………………………………………..

`9) ( x^2 - 36 )/( 2x + 10 ) . 3/( 6 - x )` ĐKXĐ `x \ne 6 ; -5`

`= (( x - 6 )( x + 6 ))/(2x + 10 ) .( -3)/( x - 6 )`

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

`10) ( x^2 - 9y^2 )/( x^2y^2 ) . ( 3xy )/( 2x - 6y )` ĐKXĐ `x ; y \ne 0 ; x \ne 3y`

`= (( x - 3y )( x + 3y ))/( xy ) . 3/( 2( x - 3y ))`

`= ( 3x + 9y )/( 2xy )`

`11) ( 2x - 4 )/(( x + 2 )^2) . ( x^2 + 2x )/( x^2 - 2x )` ĐKXĐ `x\ne 0 ; +-2`

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

`= 2/( x + 2)`

`12) ( x^2 + 2x + 1 )/( x^2 - 1 ) . ( x^2 - x )/( x + 1 )` ĐKXĐ `x \ne +- 1`

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

`= x`

`13) ( 6x - 3x^2 )/( x^2 - 4x + 4 ) . ( 5x - 10 )/( 3x )` ĐKXĐ `x \ne 0 ; 2`

`= ( 3x( 2 - x ))/(( x - 2 )^2) . ( 5( x - 2))/( 3x )`

`= ( 2 - x )/( x - 2 ) . 5`

`= -5`