Question
Expand :$\left(x+\frac{1}{x}\right)\left(x-\frac{1}{x}\right)$
✓
Answer
$\begin{aligned} & \text {}\left(x+\frac{1}{x}\right)\left(x-\frac{1}{x}\right) \\ & =x^2+\left(\frac{1}{x}-\frac{1}{x}\right) x+\frac{1}{x} \times\left(-\frac{1}{x}\right) \\ & \quad \ldots\left[\because(x+\mathrm{a})(x+\mathrm{b})=x^2+(\mathrm{a}+\mathrm{b}) x+\mathrm{ab}\right] \\ & =x^2+0 \times x-\frac{1}{x^2} \\ & =x^2-\frac{1}{x^2}\end{aligned}$
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