1、计算x-y+2y²/x+y2、请你先化简1/a+3+6/a²-9,再选取一个使原式有意义代入求值

1、计算x-y+2y²/x+y2、请你先化简1/a+3+6/a²-9,再选取一个使原式有意义代入求值
1、计算x-y+2y²/x+y
2、请你先化简1/a+3+6/a²-9,再选取一个使原式有意义代入求值

1、计算x-y+2y²/x+y2、请你先化简1/a+3+6/a²-9,再选取一个使原式有意义代入求值
1、[(x-y)(x+y)+2y²]/(x+y)
=(x²-y²+2y²)/(x+y)
=(x²+y²)/(x+y)
2、原式=(a-3)/(a+3)(a-3)+6/(a+3)(a-3)
=(a-3+6)/(a+3)(a-3)
=1/(a-3)