过抛物线y^2=4x的焦占作直线交抛物线于A(x1, y1), B(x2, y2)两点,如果x1+x2=2，那么|AB|的长是

焦点坐标是(1,0).
设直线方程是y=k(x-1)
所以有:k^2(x-1)^2=4x.
k^2x^2-(2k^2+4)x+k^2=0
x1+x2=(2k^2+4)/k^2=6
2k^2+4=6k^2
k^2=1.
k=(+/-)1.即倾斜角是45或135度.
x1x2=k^2/k^2=1
(x1-x2)^2=(x1+x2)^2-4x1x2=36-4=32
|x1-x2|=4根号2.
即AB=|x1-x2|/根号2=4.