6y2 - 24y - 4y +16 = 7y2 - 28y - 84
6y2 - 24y - 4y - 7y2 +28y = -100
-y2 = -100
y=10
4•4(-10+9)-5•4(-8-3)=-8+220=212
А) 18а+(а-9)² = 18а+а²-18а+81 = а²+81
б) (5х-1)²-25х² = 25х²-10х+1-25х² = -10х+1
в) 4х²-(2х-3)² = 4х²-4х²+12х-9 = 12х-9
г) (а+2b)²-4b² = a²+4ab+4b²-4b² = a²+4ab