№284
1)(с-4)(d-3)=cd-3c-4d+12
2)(a-10)(-a-2)=-a²-2a+10a+20=-a²+8a+20
3)(x+y)(x+1)=x²+x+xy+y
4)(-p+q)(-1-q)=p+pq-q-q²
№285
1)(2x+1)(x+4)=2x²+8x+x+4=2x²+9x+4
2)(2a+3)(5a-4)=10a²-8a+15a-12=10a²+7a-12
3)(3m-2)(2m-1)=6m²-3m-4m+2=6m²-7m+2
4)(5p-3q)(4p-q)=20p²-5pq-12pq+3q²=20p²-17pq+3q²
