化简求值:x/[9(x-y)^2]*[(x^2-y^2)/(x+y)]+{[(x^2+2)/(x+y)]-2}

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化简求值:x/[9(x-y)^2]*[(x^2-y^2)/(x+y)]+{[(x^2+2)/(x+y)]-2}
已知某轮船顺水航行a千米所需的时间和逆水航行b所需的时间相同。若水流的速度为c千米/时，则船在静水中的速度为（此题为填空题）我把悬赏+5分吧！

1、
x/9(x-y)^2 *(x-y)+(x^2+2-x-y)/(x+y)
=x/9(x-y)+(x^2+2)/(x+y)-2
=[(x(x+y)+9(x-y)(x^2+2)]/9(X-Y)(X+Y)-2
=[X^2+XY+9X^3+18X-9X^2Y-18XY]/9(X^2-Y^2)-2
=[X(9X^2+X+18)+XY(9X-7)]/9(X^2-Y^2)-2
2、
X
(X+c)*t=a
(X-c)*t=b
(X+c)/(X-c)=a/b
aX-ac=bX+bc
c(a+b)=X(b-a)
X=c(a+b)/(b-a)
即为所求船在静水中的速度

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