Rationalisation Method

Rarely Tested

Rationalisation Method

For expressions involving radicals, multiply by the conjugate expression.

For example:

$$\sqrt{f(x)}-\sqrt{g(x)}$$

can be rationalised using:

$$\left(\sqrt{f(x)}-\sqrt{g(x)}\right)\left(\sqrt{f(x)}+\sqrt{g(x)}\right)=f(x)-g(x)$$

Usage

- Used to remove radicals and resolve indeterminate forms such as $$\frac{0}{0}$$.

Question 1

Let $$\alpha_n$$ be the smaller root of the equation $$x^2-(2n+1)x+\frac{n(n+1)}2=0.$$ If $$L=\lim_{n\to\infty}\frac{\alpha_n}{\sqrt2\,n+1},$$ then the value of $$\lfloor8L\rfloor$$ is 

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