约分a²-ab+b²/a³+b³ x²-xy-2y²/x²-3xy+2y²通分3x/1-x²,-2x+1/x²-3x+2,1-x/2x-x²+3尽量用初二的知识作答

约分a²-ab+b²/a³+b³ x²-xy-2y²/x²-3xy+2y²通分3x/1-x²,-2x+1/x²-3x+2,1-x/2x-x²+3尽量用初二的知识作答
约分a²-ab+b²/a³+b³ x²-xy-2y²/x²-3xy+2y²
通分
3x/1-x²,-2x+1/x²-3x+2,1-x/2x-x²+3
尽量用初二的知识作答

约分a²-ab+b²/a³+b³ x²-xy-2y²/x²-3xy+2y²通分3x/1-x²,-2x+1/x²-3x+2,1-x/2x-x²+3尽量用初二的知识作答
a³+b³=（a²-ab+b²）*（a+b）
x²-xy-2y²=（x+y)*(x-2y)
x²-3xy+2y²=(x-y)*(x-2y)