y1-3与x成正比例
则y1-3=k1x
y1=k1x+3
y2与x²成反比例
y2=k2/x²
y=y1+y2=k1x+3+k2/x²
当x=1时,y1=y2
k1*1+3=k2/1²
k1+3=k2
y=k1x+3+(k1+3)/x²
x=2时,y=6
6=k1*2 + 3 +(k1+3)/2²
6=2k1+3+(k1+3)/4
24=8k1+12+k1+3
9k1=9
k1=1
k2=k1+3=1+3=4
y=k1x+3+(k1+3)/x²
=x+3+(1+3)/x²
=x+3+4/x²
x=-1时
y=-1+3+4/(-1)²
=2+4
=6