1.[(a+b)²-3ab][(a-b)²+3ab]
问题描述：
1.[(a+b)²-3ab][(a-b)²+3ab]
2.(x+y+z)(x+y-z)-(x-y+z)(x+y-z)
3.已知x=2,y=-4时,代数式ax³+1/2by+5=1997,当x=-4,y=-2时,求代数式3ax-24by³+4986的值.
答
1.[(a+b)²-3ab][(a-b)²+3ab]
=[a^2+b^2-ab][a^2+b^2+ab]
=(a^2+b^2)^2-(ab)^2
2.(x+y+z)(x+y-z)-(x-y+z)(x+y-z)
=(x+y-z)[(x+y+z)-(x-y+z)]
=(x+y-z)(2y)
=2y(x+y-z)
3.已知x=2,y=-4时,8a-2b+5=1997
x=-4,y=-2时,-64a-b+5=1997
得到：a=,b=最后一道题可以写完么???谢谢！还没有写完哦，麻烦补全一下可以吗????对对对。 后面的是y=-1/2