Toán Lớp 9: 1/ √x+3 – √x-3/x-9
giúp mình vs ạ
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Toán Lớp 9: 1/ √x+3 – √x-3/x-9
giúp mình vs ạ
Comments ( 2 )
Giải đáp+Lời giải và giải thích chi tiết:
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)
$\dfrac{\sqrt{x}-3}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}-\dfrac{\sqrt{x}-3}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}$
$\dfrac{\sqrt{x}-3-\sqrt{x}+3}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}$
$=\dfrac{0}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}$
$=0$