1)-2(3a-b)+6a=-2*3-(-2)*b+6a=-6a+2b+6a=2b
(m-2n)^2+4mn=m^2-4mn+4n^2+4mn=m^2+4n^2
(x-6y)(x+6y)+9(2y)^2=x^2-(6y)^2+9*4y^2=x^2-36y^2+36y^2=x^2
4(3x-2y)+8y=4*3x-4*2y+8y=12x-8y+8y=12x
6xy-(x+3y)^2=6xy-(x^2+2*3xy+(3y)^2)=6xy-x^2-6xy-9y^2=-x^2-9y^2
(a+8b)(-a+8b)-4(4b)^2=(8b)^2-a^2-4(16b)^2=64b^2-a^2-64b^2=-a^2
6m-3(2m-5n)=6m-3*2m+3*5n=6m-6m+15n=15n
4a^2-(b-2a)^2=(2a-(b-2a))(2a+(b-2a))=(2a-b+2a)(2a+b-2a)=(4a-b)b
-4(3a)^2+(6a-5c)(6a+5c)=-4*9a^2+36a^2-25c^2=-36a^2+36a^2+25c^2=25c^2
2) ab-cb=b(a-c)
4a^2b-6ab^2=2ab(2a-3b)
25x^2-16y^2=(5x-4y)(5x+4y)
9m^2-12mn+4n^2=(3m-2n)^2
8x+6y=2(4x+3y)
-15x^3y^2+18xy^4=3xy^2(-5x^2+6y^2)
64m^2-49n^2=(8m-7n)(8m+7n)
25a^2+40ab+16b^2=(5a+4b)^2
a^2x-a^2y=a^2(x-y)
1.2a^5b^3-2.4a^3b^5=1.2a^3b^3(a^2-2b^2)
-x^2+y^2=y^2-x^2=(y-x)(y+x)
-2mn+m^2n^2=m^2-2mn+n^2=(m-n)^2