Rút gọn: `a)2/(x^2-y^2)*sqrt{(9(x^2+2xy+y^2))/(4)` Với `x ne +-y`  `b)1/(2a-1)*sqrt{25a^4-100a^5+100a^6` Với `a ne 1/2`

`a) 2/(x^2-y^2) . sqrt{(9(x^2+2xy+y^2))/4}`   `(x ne +- y)`

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

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

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

`= 3/(x-y)`

`b) 1/(2a-1). sqrt{25a^4 -100a^5 +100a^6}`   `(a ne 1/2)`

`= 1/(2a-1). sqrt{(5a^2)^2 -2.5a^2 .10a^3 +(10a^3)^2}`

`= 1/(2a-1). sqrt{(5a^2 +10a^3)^2}`

`= 1/(2a-1). |5a^2 + 10a^3|`