rút gọn với x lớn hơn hoặc bằng 0

`c) 2/( x^2 - y^2 ) . \sqrt{ ( 3 ( x + y )^2 )/2}`

`= 2/( ( x - y ) ( x + y ) ) . \sqrt{ [ \sqrt{3} ( x + y ) ]^2/( \sqrt{2} )^2}`

`= 2/( ( x - y ) ( x + y ) ) . ( \sqrt{3} . ( x + y ) )/( \sqrt{2} )`

`= ( 2 \sqrt{3} )/( \sqrt{2} ( x - y ) )`

`= \sqrt{6}/( x - y )`