Rút gọn( giả sử mọi đkiện thỏa mãn: (√(2x+1)/(√(x^3 )-1) – √x/(x+1+√x) ) . ( (1+√(x^3 ))/(1+√x) – √x). giúp e với ạ 03/10/2021 Bởi Lydia Rút gọn( giả sử mọi đkiện thỏa mãn: (√(2x+1)/(√(x^3 )-1) – √x/(x+1+√x) ) . ( (1+√(x^3 ))/(1+√x) – √x). giúp e với ạ
Ta co $(\dfrac{\sqrt{2x+1}}{\sqrt{x^3}-1} – \dfrac{\sqrt{x}}{x + 1 + \sqrt{x}}) .(\dfrac{1 + \sqrt{x^3}}{1 + \sqrt{x}} – \sqrt{x})$ $= (\dfrac{\sqrt{2x+1}}{\sqrt{x^3}-1} – \dfrac{\sqrt{x}(\sqrt{x}-1)}{(\sqrt{x}-1)(x + 1 + \sqrt{x}}) .(\dfrac{(1 + \sqrt{x})(x – \sqrt{x}+1)}{1 + \sqrt{x}} – \sqrt{x})$ $= \dfrac{\sqrt{2x+1} – (x-\sqrt{x})}{\sqrt{x^3}-1} . (x – 2\sqrt{x} + 1)$ $= \dfrac{\sqrt{2x+1} – x+\sqrt{x}}{(\sqrt{x} – 1)(x + \sqrt{x} + 1)} . (\sqrt{x}-1)^2$ $= \dfrac{\sqrt{2x+1} – x+\sqrt{x}}{x + \sqrt{x} + 1} . (\sqrt{x}-1)$ Bình luận
Ta co
$(\dfrac{\sqrt{2x+1}}{\sqrt{x^3}-1} – \dfrac{\sqrt{x}}{x + 1 + \sqrt{x}}) .(\dfrac{1 + \sqrt{x^3}}{1 + \sqrt{x}} – \sqrt{x})$
$= (\dfrac{\sqrt{2x+1}}{\sqrt{x^3}-1} – \dfrac{\sqrt{x}(\sqrt{x}-1)}{(\sqrt{x}-1)(x + 1 + \sqrt{x}}) .(\dfrac{(1 + \sqrt{x})(x – \sqrt{x}+1)}{1 + \sqrt{x}} – \sqrt{x})$
$= \dfrac{\sqrt{2x+1} – (x-\sqrt{x})}{\sqrt{x^3}-1} . (x – 2\sqrt{x} + 1)$
$= \dfrac{\sqrt{2x+1} – x+\sqrt{x}}{(\sqrt{x} – 1)(x + \sqrt{x} + 1)} . (\sqrt{x}-1)^2$
$= \dfrac{\sqrt{2x+1} – x+\sqrt{x}}{x + \sqrt{x} + 1} . (\sqrt{x}-1)$