a)(3a+b)+(5a-4b)-(8a+9b)=3a+b+5a-4b-8a-9b=-12b
Б) x-(2x-y)+(3x-2y)=x-2x+y+3x-2y=2x-y
в)(8c^2 +3с)+(-7c^2 -11с+3)-(-3с^2-4)=8c^2+3c-7c^2-11c+3+3c^2+4=4c^2-8c+7
г)(a-b+c)+(a-c)-(a-b-c)=a-b+c+a-c-a+b+c=a+c
a)(3a+b)+(5a-4b)-(8a+9b)=3a+b+5a-4b-8a-9b=-12b
Б) x-(2x-y)+(3x-2y)=x-2x+y+3x-2y=2x-y
в)(8c^2 +3с)+(-7c^2 -11с+3)-(-3с^2-4)=8c^2+3c-7c^2-11c+3+3c^2+4=4c^2-8c+7
г)(a-b+c)+(a-c)-(a-b-c)=a-b+c+a-c-a+b+c=a+c