Question

已知y=y1-2y2,y1与x2成反比例,y2与x成正比例,且当x=﹣1时,y=5；当x=1时.y=-1

Answer 1

因为y1与x²成反比例

所以设y1 = k/x²

因为y2与x成正比例

所以设y2 = mx

所以y = y1 - y2 = k/x² - mx

把x = -1,y = 5；x = 1,y = -1代入得

5 = k + m

-1 = k - m

解得k = 2,m = 3

所以y = 2/x² - 3x