Question

cho biểu thức

A=\(\dfrac{\sqrt{x}\left(\sqrt{x^3-1}\right)}{x+\sqrt{x}+1}-\dfrac{2x+\sqrt{x}}{\sqrt{x}}+\dfrac{2\left(x-1\right)}{\sqrt{x}-1}\) x>0,x≠1

a.Rút gọn biểu thức A

b.Tìm x để giá trị A=\(\dfrac{3}{4}\)

Answer 1

a) A=\(\dfrac{\sqrt{x}[\left(\sqrt{x}\right)^3-1]}{x+\sqrt{x}+1}-\dfrac{2x+\sqrt{x}}{\sqrt{x}}+\dfrac{2\left(x-1\right)}{\sqrt{x}-1}\)

A=\(\dfrac{\sqrt{x}\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}{x+\sqrt{x}+1}-\dfrac{\sqrt{x}\left(2\sqrt{x}+1\right)}{\sqrt{x}}+\dfrac{2\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}{\sqrt{x}-1}\) A=\(\sqrt{x}\left(\sqrt{x}-1\right)-2\sqrt{x}-1+2\sqrt{x}+2\)

A=\(x-\sqrt{x}+1\)

b) A=\(\dfrac{3}{4}\)

=> \(x-\sqrt{x}+1=\dfrac{3}{4}\)

\(x-\sqrt{x}+\dfrac{1}{4}=0\)

\(\left(\sqrt{x}-\dfrac{1}{2}\right)^2=0\)

=> \(\sqrt{x}=\dfrac{1}{2}\)

=> \(x=\dfrac{1}{4}\)