9(d) is very tricky......
x - 2 + 1/x is exactly in the form of a2 - 2ab + b2 , Therefore we can factor it as (a-b)2 .
x - 2 + 1/x = \((\sqrt x - \dfrac{1}{\sqrt x})^2\)
x - 1/x is exactly in the form of a2 - b2 . Therefore we can factor it as (a+b)(a-b)
x - 1/x = \((\sqrt x - \dfrac{1}{\sqrt x})(\sqrt x + \dfrac{1}{\sqrt x})\)
The original fraction became:
\(\dfrac{(\sqrt x - \frac{1}{\sqrt x})(\sqrt x - \frac{1}{\sqrt x})}{(\sqrt x + \frac{1}{\sqrt x})(\sqrt x - \frac{1}{\sqrt x})}\)
Did you see any same parts on the denominator and the numerator?
The hardest part is already solved by me.
And don't forget to multiply both the denominator and the numerator by \(\sqrt x\) because we don't want \(\dfrac{1}{\sqrt x}\) to appear in a fraction.
Final answer: \(\dfrac{x-1}{x+1}\)
Try to figure out why.
这个论坛终于有懂中文的人了 :D
我一直不知道马来西亚用简体。 香港是用繁体的, 不过不要紧, 我能看得懂简体中文。