Factorise $a^{2} + \dfrac{1}{a^{2}} + 2$ (for $a \ne 0$).
Factorise $a^{2} + \dfrac{1}{a^{2}} + 2$ (for $a \ne 0$).
- $\left(a + \dfrac{1}{a}\right)^{2}$
- $\left(a - \dfrac{1}{a}\right)^{2}$
- $\left(a + \dfrac{1}{a}\right)\left(a - \dfrac{1}{a}\right)$
- $\dfrac{a^{2}+1}{a^{2}}$
Solution
$a^{2}+\dfrac{1}{a^{2}}+2 = a^{2}+2 \cdot a \cdot \dfrac{1}{a}+\left(\dfrac{1}{a}\right)^{2} = \left(a+\dfrac{1}{a}\right)^{2}$.
Asked in: IMO
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