2. (x – y )(x + y)

3. (c – d )(c + d )

4. ( e + f)(e – f )

5. (g + h)(g – h )

6. (k + m)(m – k)

7. (3a – 4в)(3a +4в)

8. (5x – 6)(6 + 5x)

9. (7y+8)(8 – 7y)

10. (9q- 10p)(9q +10p)

11. (12r +13s)(13s – 12r)
с объяснением