两道先化简再求值的题求帮忙rt

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两道先化简再求值的题求帮忙rt两道先化简再求值的题求帮忙rt两道先化简再求值的题求帮忙rt1、原式=2x/(x²-y²)-x/(x²-y²)+y/(x+y)(x

两道先化简再求值的题求帮忙rt
两道先化简再求值的题求帮忙

rt

两道先化简再求值的题求帮忙rt
1、原式=2x/(x²-y²)-x/(x²-y²)+y/(x+y)(x-y)
=(2x-x+y)/(x+y)(x-y)
=1/(x-y)
当x=4,y=-3时
原式=1/(4+3)=1/7
2、=[2+1/(a-1)-1/(a+1)]×(a+1)(a-1)/a³
=[2(a+1)(a-1)+(a+1)-(a-1)]/(a+1)(a-1) ×(a+1)(a-1)/a³
=2/a
当a=2时
原式=1