Đáp án:
`x>=4/3 ->3x-4 >=0`
`a, 3x + \sqrt{16 - 24x + 9x^2} ( x>= 4/3)`
`= 3x + \sqrt{(3x-4)^2} ( x>= 4/3)`
`= 3x + |3x-4| ( x>= 4/3)`
`= 3x + 3x - 4 ( x>= 4/3)`
`= 6x-4 ( x>= 4/3)`
`b, 3x \sqrt{(4y^4)/(x^2)} (x<0)`
`= 3x . \sqrt{(2y)^2/x^2} (x<0)`
`= 3x . |(2y^2)/x| (x<0)`
`= 3x . (2y^2)/(-x) (x<0)`
`= -6y^2 (x<0)`
`(x<y -> x-y < 0)`
`d, (x-y)^2 \sqrt{4/(x^2-2xy+y^2)} (x<y)`
`= (x-y)^2 . \sqrt{4/(x-y)^2}`
`= (x-y)^2 . |2/(x-y)| (x-y < 0)`
`= (x-y)^2 . (-2)/(x-y) `
`= -2(x-y)`
$\text{#Dream}$
