1. y^2+12y+36
2. 4y^2-28y+49
3. 121b^2-0,04a^2
4. (7a-3b)^2
5. 9a^2-b^2+b^2=9a^2
6. b^2+8bc+16c^2+b^2-25c^2=2b^2+8bc-9c^2
7. x^2-12x+36=x^2-5x
x^2-12x+5x-x^2=-36
-7x=-36
x=36/7
x=5 1/7
8. x^2-7x=4+4x+x^2
4x+7x=-4
11x=-4
x=-4/11
9. 49^2=(50-1)^2=2500-100+1=2401