1:(ab+cd)(a²-b²+c²-d²)+(ac+bd)(a²+b²-c²-d²)

问题描述:

1:(ab+cd)(a²-b²+c²-d²)+(ac+bd)(a²+b²-c²-d²)
2:x四次方+2000x²+1999x+2000
3:x²+xy-6y²+x+13y-6
4:x²-2xy+y²-3y+2

1:(ab+cd)(a²-b²+c²-d²)+(ac+bd)(a²+b²-c²-d²)= (ab+cd)(a²-d²)+(ab+cd)(c²-b²)+(ac+bd)(a²-d²)+(ac+bd)((b²-c²)= (a²-d&...