1)4с(с-2)-(с-4)^2=4c2-8c-c2+4c-16=3c2-4c-16
2)3a(a+2)-(a+3)^2=3a2+6a-a2-3a-9=2a2+3a-9
3)3(y-1)^2+6y=3y2-3y+3+6y=3y2+3y+3
4)8c+4(1-c)^2=8c+4-4c+c2=c2+4c+4
5)4ab+2(a-b)^2=4ab+2a2-2ab+b2=2ab+2a2+b2
6)3(x+y)^2-6xy=3x2+3xy+3y2-6xy=3x2-3xy+3y2
7)3a(a-2)-(a-3)^2=3a2-6a-a2+3a-9=2a2-3a-9
8)(a-4)^2-2a(3a-4)=a2-4a+16-6a2+8a=8a-5a2+16
9)(x-y)^2-x(x-2y)=x2-xy+y2-x2+2xy=xy+y2
10)a(a+2b)-(a+b)^2=a2+2ab-a2-ab-b2=ab-b2
11)(a-3)(a-7)-2a(3a-5)=a2-7a-3a+21-6a2+10a=21-5a2
12)(x-2)(x+4)-2x(1+x)=x2+4x-2x-8-2x-2x2=-x2-8
13)2c(3c+4)-3c(2c+1)=6c2+8c-6c2-3c=5c
14)3a(2a-1)-2a(4+3a)=6a2-3a-8a-6a2=-11a