(x-y)/(x²-xy-2y²) - 2/(3x+3y)
题目
(x-y)/(x²-xy-2y²) - 2/(3x+3y)
答案
(x-y)/(x^2-xy-2y^2) - 2/(3x+3y)
=(x-y)/[(x+y)(x-2y)]-2/[3(x+y)]
=(3x-3y)/[3(x+y)(x-2y)]-(2x-4y)/[3(x+y)(x-2y)]
=(3x-3y-2x+4y)/[3(x+y)(x-2y)]
=(x+y)/[3(x+y)(x-2y)]
=1/[3x-6y]
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