а) a(b+3)+b(a+3)-3(a+b) = ab + 3a + ba + 3b - 3a - 3b = 2ab
б) 2(x-y)+6(y-x)-(4x-4y) = 2x - 2y + 6y - 6x - 4x + 4y = -8x + 8y
в) a(b+c)-b(a+c)-c(a+b) = ab + ac - ab - bc - ac - ab = -bc
г) m(n-l)+n(l-m)+l(m-n) = mn - ml + nl - nm + lm - ln = 0
а) a(b+3)+b(a+3)-3(a+b) = ab + 3a + ba + 3b - 3a - 3b = 2ab
б) 2(x-y)+6(y-x)-(4x-4y) = 2x - 2y + 6y - 6x - 4x + 4y = -8x + 8y
в) a(b+c)-b(a+c)-c(a+b) = ab + ac - ab - bc - ac - ab = -bc
г) m(n-l)+n(l-m)+l(m-n) = mn - ml + nl - nm + lm - ln = 0