**(i) a ^{4} – b^{4} + 2b^{2} – 1**

**(ii) x ^{3} – 25x**

**Answer :**

**(i) a**^{4} – b^{4} + 2b^{2} – 1

^{4}– b

^{4}+ 2b

^{2}– 1

Above terms can be written as,

a^{4} – (b^{4} – 2b^{2} + 1)

We know that, (a – b)^{2} = a^{2} – 2ab + b^{2}

a^{4} – ((b^{2})^{2}) – (2 × b^{2} × 1) + 1^{2})

(a^{2})^{2} – (b^{2} – 1)^{2}

We know that, a^{2} – b^{2} = (a + b) (a – b)

(a^{2} + b^{2} – 1) (a^{2} – b^{2} + 1)

**(ii) x**^{3} – 25x

^{3}– 25x

x^{3} – 25x

Take out common in all terms,

x(x^{2} – 25)

Above terms can be written as,

x(x^{2} – 5^{2})

We know that, a^{2} – b^{2} = (a + b) (a – b)

x(x + 5) (x – 5)

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