Question

\(A=\dfrac{\sqrt{x}-1}{\sqrt{x}-3}\)

Tính A biết \(x=4-2\sqrt{3}\)

Answer 1

ta có:\(x=4-2\sqrt{3}=\left(\sqrt{3}-1\right)^2\)

thay x=\(\left(\sqrt{3}-1\right)^2\) vào A ta có

A=\(\dfrac{\sqrt{\left(\sqrt{3}-1\right)^2}-1}{\sqrt{\left(\sqrt{3}-1\right)^2}-3}=\dfrac{\sqrt{3}-1-1}{\sqrt{3}-1-3}\)

A=\(\dfrac{\sqrt{3}-2}{\sqrt{3}-4}\)