Question

已知y=y1+ y2,y1与x成正比例,y2与x平方成反比,且x=1,y=3；x=-1,y=1,求x=-1/2时,y的值

Answer 1

y1=k1x

y2=k2/x²

y=k1x+k2/x²

x=1 y=3

3=k1*1+k2/1²

k1+k2=3.(1)

x=-1 y=1

1=k1(-1)+k2/(-1)²

-k1+k2=1.(2)

(1)+(2)：2k2=4

k2=2

代入(1)：k1+2=3

k1=1

y=x+2/x²

x=-1/2

y=-1/2+2/(-1/2)²

=-1/2+8

=15/2