1) x2-7x-3x+21-6x2+10x=-5x2+21
2) 4a2-8a-(a2-8a+16)=5a2-16
3) 2(t2+2t+1)-4t= 2t2+4t+2-4t=2t2+2
Объяснение:
1) x2-7x-3x+21-6x2+10x=-5x2+21
2) 4a2-8a-(a2-8a+16)=5a2-16
3) 2(t2+2t+1)-4t= 2t2+4t+2-4t=2t2+2
Объяснение: