帮下忙,初4二次函数抛物线y=1/2x^2-3/2mx-2m交X轴A(X1,0)B(X2,0)交Y轴于点C且x1

Question

帮下忙,初4二次函数
抛物线y=1/2x^2-3/2mx-2m 交X轴A(X1,0)B(X2,0)交Y轴于点C且x1

Answer 1

点C（0,-2m）；OC=|2m|;
交于三点,则可知-2m<0;
m>0;
则OC=2m;
OA+OB=x2-x1,
则(OA+OB)^2=(x2-x1)^2= (x2+x1)^2 -4·x1·x2 = （3m）^2 +16m
=24m+1;
→9m^2 +8m -1 =0;
m=1/9;
则解析式为
y=1/2x^2-1/6x-2/9