Question 19: Factoring polynomials
\(x^{4}-4\left(x^{2}+5\right)-25\)
\(\begin{aligned} &=\left(x^{4}-25\right)-4\left(x^{2}+5\right) \\ &=\left(x^{2}+ 5\right)\left(x^{2}-5-4\right) \\ &=\left(x^{2}+5\right)\left(x^{2}-9\right) \ \ &=\left(x^{2}+5\right)(x-3)(x+3) \end{aligned}\)
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