若X+3Y=0,XY≠0 求X²-3XY/XY+Y²的值
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![若X+3Y=0,XY≠0 求X²-3XY/XY+Y²的值](/uploads/image/z/8612391-39-1.jpg?t=%E8%8B%A5X%2B3Y%3D0%2CXY%E2%89%A00+%E6%B1%82X%26sup2%3B-3XY%2FXY%2BY%26sup2%3B%E7%9A%84%E5%80%BC)
若X+3Y=0,XY≠0 求X²-3XY/XY+Y²的值
若X+3Y=0,XY≠0 求X²-3XY/XY+Y²的值
若X+3Y=0,XY≠0 求X²-3XY/XY+Y²的值
x+3y=0 => x=-3y => x/y=-3
原式= (x^2-3xy)/(xy+y^2) 上下各除个y^2
= [(x/y)^2-3(x/y)]/[(x/y)+1] 代入x/y=-3
= [(-3)^2-3(-3)]/[-3+1]
= -9