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Đáp án:

`a,A=11/2\sqrt{x}`

`b,B=-y-3/4`

Giải thích các bước giải:

`a,A=4\sqrt{(25x)/(4)}-8/3\sqrt{(9x)/(4)}-4/(3x)\sqrt{(9x^2)/(64)}`

`=4\sqrt{(25)/(4).x}-8/3\sqrt{(9)/(4).x}-4/(3x)\sqrt{(9)/(64).x^3}`

`=4\sqrt{(25)/(4)}\sqrt{x}-8/3\sqrt{(9)/(4)}\sqrt{x}-4/(3x)\sqrt{(9)/(64)}\sqrt{x^3}`

`=4.(5)/(2)\sqrt{x}-8/3.(3)/(2)\sqrt{x}-4/(3x).(3)/(8)x\sqrt{x}`

`=10\sqrt{x}-4\sqrt{x}-1/2\sqrt{x}`

`=11/2\sqrt{x}`

Vậy `A=11/2\sqrt{x}`

`b,B=y/2+3/4\sqrt{1-4y+4y^2}-3/2`

`=1/2y+3/4\sqrt{(1-2y)^2}-3/2`

`=1/2y+3/4|1-2y|-3/2`

Mà `y<=1/2⇒1-2y>=0`

`⇒|1-2y|=1-2y`

`⇒B=1/2y+3/4.(1-2y)-3/2`

`=1/2y+3/4-3/2y-3/2`

`=-y-3/4`

Vậy `B=-y-3/4`