Factorise

1)

x^{2} + 0 x - 4

(x + 2) (x - 2)

2)

x^{2} + 0 x - 16

(x + 4) (x - 4)

3)

x^{2} - 0 x - 225

(x + 15) (x - 15)

4)

x^{2} - 100

(x + 10) (x - 10)

5)

x^{2} - 1

(x + 1) (x - 1)

6)

x^{2} - \frac{1}{25}

(x + \frac{1}{5}) (x - \frac{1}{5})

7)

x^{2} - y^{2}

(x + y) (x - y)

8)

x^{2} - 2

(x + \sqrt{2}) (x - \sqrt{2})