Đáp án+Giải thích các bước giải:
`a)A=(sqrt(20)-sqrt(45)+3sqrt5):sqrt5`
`=(sqrt{4.5}-sqrt{9.5}+3sqrt5):sqrt5`
`=(2sqrt5-3sqrt5+3sqrt5):sqrt5`
`=2sqrt5:sqrt5`
`=2`
`B=(x+2sqrtx)/sqrtx+(x-9)/(sqrtx+3)(x>0)`
`=(sqrtx(sqrtx+2))/sqrtx+((sqrtx-3)(sqrtx+3))/(sqrtx+3)`
`=sqrtx+sqrtx-3`
`=2sqrtx-3`
`b)B=A`
`<=>2sqrtx-3=2`
`<=>2sqrtx=5`
`<=>sqrtx=5/2`
`<=>x=25/4(tmđk)`
Vậy với `x=25/4` thì `A=B.`