1. x^2+4x+4

2.9x^2-20xy+25y^2

3.16x^4-16ax^2+4a^2

4.1/9x^4+5/3yx^2+25/4y^2

5. 17,64a^2-10,08ay+1,44y^2

6.100/9 a^2 +100/3 ay +25y^2

7. a^2-1/9y^2

8. 16y^2-25x^2

9. 6,25x^4-16y^6

10.4x^2+12xy+9y^2-x^2+y^2+25x^2-40xy+16y^2=28x^2-28xy+26y^2=2(14x^2+14xy+13y^2)