设A(x1,y1),B(x2,y2) 则|AB|^2=(x1-x2)^2+(y1-y2)^2=20
将直线方程与抛物线方程联立方程组
解得(x1-x2)^2=1-2m
(y1-y2)^2=4(1-2m) |AB|^2=(x1-x2)^2+(y1-y2)^2=1-2m+4(1-2m)=5(1-2m)=20
解得m=-3/2
设A(x1,y1),B(x2,y2) 则|AB|^2=(x1-x2)^2+(y1-y2)^2=20
将直线方程与抛物线方程联立方程组
解得(x1-x2)^2=1-2m
(y1-y2)^2=4(1-2m) |AB|^2=(x1-x2)^2+(y1-y2)^2=1-2m+4(1-2m)=5(1-2m)=20
解得m=-3/2