2 câu trả lời
Đáp án+Giải thích các bước giải:
`1/(sqrtx+3)-(sqrtx-3)/(x-9)` ĐK: `x>=0; x\ne9`
`=(sqrtx-3)/((sqrtx-3)(sqrtx+3))-(sqrtx-3)/((sqrtx-3)(sqrtx+3))`
`=(sqrtx-3-sqrtx+3)/((sqrtx-3)(sqrtx+3))`
`=0/((sqrtx-3)(sqrtx+3))`
`=0`
$\dfrac{1}{\sqrt{x}+3\:}-\dfrac{\sqrt{x}-3}{9}$ $;$ ĐK: `(x≥0 ; x≠9)`
$\dfrac{\sqrt{x}-3}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}-\dfrac{\sqrt{x}-3}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}$
$\dfrac{\sqrt{x}-3-\sqrt{x}+3}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}$
$=\dfrac{0}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}$
$=0$