A:成正比例
B:成反比例
C:不成比例
be aware of, (be)scared to death, upside down, at close range, wake up, be fond of, get close to, in danger of
若对于实数a,b,规定a*b=a2-aba≥bab-a2a<b,例如:2*3,因2<3,所以2*3=2×3﹣22=2.若x1,x2是方程x2﹣2x﹣3=0的两根,则x1*x2=____ .