直线2x+y-3=0即 y=3-2x代入抛物线方程 x²=-4y即 x²=-4(3-2x)∴ x²-8x+12=0∴ (x-2)(x-6)=0∴ x=2,x=6即交点A(2,-1),B(6,-9)∴ 弦长|AB|=√[(2-6)²+(-1+9)²]=√80=4√5...