giúp nhẹ cái $\frac{a√a+27}{a-3√a+9}$ – $\frac{a}{√a-3}$ 11/09/2021 Bởi Madelyn giúp nhẹ cái $\frac{a√a+27}{a-3√a+9}$ – $\frac{a}{√a-3}$
Điều kiện: $a\ge 0; a\ne 9$ $\dfrac{\sqrt{a}^3+3^3}{(\sqrt{a})^2-3\sqrt{a}+3^2}-\dfrac{a}{\sqrt{a}-3}$ $=\dfrac{(\sqrt{a}+3)[(\sqrt{a})^2-3\sqrt{a}+3^2]}{ (\sqrt{a})^2-3\sqrt{a}+3^2}-\dfrac{a}{\sqrt{a}-3}$ $=\sqrt{a}+3-\dfrac{a}{\sqrt{a}-3}$ $=\dfrac{(\sqrt{a}+3)(\sqrt{a}-3)-a}{\sqrt{a}-3}$ $=\dfrac{a-9-a}{\sqrt{a}-3}$ $=\dfrac{-9}{\sqrt{a}-3}$ Bình luận
Điều kiện: $a\ge 0; a\ne 9$
$\dfrac{\sqrt{a}^3+3^3}{(\sqrt{a})^2-3\sqrt{a}+3^2}-\dfrac{a}{\sqrt{a}-3}$
$=\dfrac{(\sqrt{a}+3)[(\sqrt{a})^2-3\sqrt{a}+3^2]}{ (\sqrt{a})^2-3\sqrt{a}+3^2}-\dfrac{a}{\sqrt{a}-3}$
$=\sqrt{a}+3-\dfrac{a}{\sqrt{a}-3}$
$=\dfrac{(\sqrt{a}+3)(\sqrt{a}-3)-a}{\sqrt{a}-3}$
$=\dfrac{a-9-a}{\sqrt{a}-3}$
$=\dfrac{-9}{\sqrt{a}-3}$