Відповідь:а) = 3(a-b)×(a-b+a)=3(a-b)×(2a-b)
б) = 3(2x×(x+y)-(x-y²))=3(2x²+2xy-(x²-2 xy+y²))=3(2x²+2xy-x²+2xy-y²)= 3(x²+4xy-y²)
в) = a²+6a+9+(-2a-16)×(a-7)=a²+6a+9-2a²+14a-16a+112= -a²+4a+121
г) = 5b+2b²-20-8b-3(1-2b+b²)= 5b+2b²-20-8b-3+6b-3b²=3b-b²-23= -b²+3b-23
