Question:
Factorise:
$4 x^{4}+7 x^{2}-2$
Solution:
$4 x^{4}+7 x^{2}-2=4 x^{4}+8 x^{2}-x^{2}-2$
$=4 x^{2}\left(x^{2}+2\right)-1\left(x^{2}+2\right)$
$=\left(4 x^{2}-1\right)\left(x^{2}+2\right)$
Hence, factorisation of $4 x^{4}+7 x^{2}-2$ is $\left(4 x^{2}-1\right)\left(x^{2}+2\right)$.
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