y-x/x²-y² a+2/a²-2a-a+4/a²-4 5/12a²-3/8ab
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y-x/x²-y²a+2/a²-2a-a+4/a²-45/12a²-3/8aby-x/x²-y²a+2/a²-2a-a+
y-x/x²-y² a+2/a²-2a-a+4/a²-4 5/12a²-3/8ab
y-x/x²-y² a+2/a²-2a-a+4/a²-4 5/12a²-3/8ab
y-x/x²-y² a+2/a²-2a-a+4/a²-4 5/12a²-3/8ab
(y-x)/(x²-y²)=-(x-y)/[(x-y)(x+y)]=-1/(x+y)
.
(a+2)/(a²-2a) - (a+4)/(a²-4)
=(a+2)/[a(a-2)] - (a+4)/[(a+2)(a-2)]
=[(a+2)²-a(a+4)]/[a(a+2)(a-2)]
=(a²+4a+4- a²-4a)/[a(a+2)(a-2)]
=4/[a(a+2)(a-2)]
.
5/12a²-3/8ab
=(1/24)a*(10a - 9b)