`cccolor{#8FBC8F}{~} cccolor{#C1FFC1}{b} cccolor{#B4EEB4}{u} cccolor{#9BCD9B}{i} cccolor{#698B69}{g} cccolor{#2E8B57}{i} cccolor{#54FF9F}{a} cccolor{#4EEE94}{p} cccolor{#43CD80}{h} cccolor{#98FB98}{o} cccolor{#008B45}{n} cccolor{#00FF00}{g} cccolor{#00EE00}{9} cccolor{#00CD00}{9} cccolor{#ADFF2F}{9} cccolor{#228B22}{~}`

`b)`

`A=3sqrt20-2sqrt45+sqrt80`

`A=3sqrt(2^2 . 5) - 2sqrt(3^2 . 5) + sqrt(4^2 . 5)`

`A=3.2 sqrt5 - 2 . 3 sqrt5 + 4sqrt5`

`A=6sqrt5-6sqrt5+4sqrt5`

`A=4sqrt5`

Vậy `A=4sqrt5`

`c)`

`P=(3sqrtx)/(sqrtx+2)+sqrtx/(2-sqrtx)+(8sqrtx)/(x-4) \ (x ge 0; x ne 4)`

`P=(3sqrtx)/(sqrtx+2)-sqrtx/(sqrtx-2)+(8sqrtx)/((sqrtx-2)(sqrtx+2))`

`P=(3sqrtx(sqrtx-2))/((sqrtx-2)(sqrtx+2))-(sqrtx(sqrtx+2))/((sqrtx-2)(sqrtx+2))+(8sqrtx)/((sqrtx-2)(sqrtx+2))`

`P=(3sqrtx(sqrtx-2)-sqrtx(sqrtx+2)+8sqrtx)/((sqrtx-2)(sqrtx+2))`

`P=(3x-6sqrtx-x-2sqrtx+8sqrtx)/((sqrtx-2)(sqrtx+2))`

`P=(2x)/(x-4)`

Vậy `P=(2x)/(x-4)`

$\color{#29B6F6}{\heartsuit Phuongg \ Li nhh \heartsuit}$