作业帮先化简再求值2x/(x²-y²)+x/(y²-x²)+y/[(x-y)(x+y)],其中x=-3,y=4
来源：学生作业帮助网 编辑：作业帮 时间：2024/11/18 07:36:49
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先化简再求值2x/(x²-y²)+x/(y²-x²)+y/[(x-y)(x+y)],其中x=-3,y=4
先化简再求值2x/(x²-y²)+x/(y²-x²)+y/[(x-y)(x+y)],其中x=-3,y=4
先化简再求值2x/(x²-y²)+x/(y²-x²)+y/[(x-y)(x+y)],其中x=-3,y=4
原式 = 2 x / （x + y）（x - y）- x /（x + y）（x - y）+ y / （x + y）（x - y）
= （2 x - x + y）/（x + y）（x - y）
= （x + y）/ （x + y）（x - y）
= 1 / （x - y）
当 x = - 3 ,y = 4 时,则原式 = 1 / （- 3 - 4）
= 1 / （- 7）
= - 1 / 7
2x/(x²-y²)+x/(y²-x²)+y/[(x-y)(x+y)]
=2x/(x²-y²)-x/(x²-y²)+y/[(x-y)(x+y)]
=(2x-x+y)/(x²-y²)
=(x+y)/(x+y)(x-y)
=1/(x-y)
当x=-3,y=4时
原式=1/(-3-4)=-1/7