1) 3x(x-2)-(x-3)^2=0
3x^2-6x-(x^2-6x+9)=0
3x^2-6x-x^2+6x-9=0
x^2=9
x=(+-)3
2) 5(a+1)^2-10a=0
5(a^2+2a+1)-10a=0
5a^2+10a+5-10a=0
5a^2=-5
a^2=1
a=(+-)1
3) 3c^2-75c=3c(c-25)
4) 3x^2+6xy+3y^2=3(x^2+2xy+y^2)
5) x^3+8=x^3+2^3
6) (y^2+6y)^2-y^2(6+5y)(6-5y)-y^2(12y-y^2)=0
y^4+12y^3-y^2(36-25y^2)-12y^3+y^4=0
y^4-36y^2+25y^4+y^4=0
27y^4-26y^2=0
7) (a-b)^2-a^2=0
a^2-2ab+b^2-a^2=0
-2ab+b^2=b(-2a+b)
8) x^3+y^3+2xy(x+y)=0
x^3+y^3+2x^2y+2xy^2=0