设A、B相距x米,A的速度为y,
B的速度为(x-100)÷(100/y)=y(100-x)/100
(x+120)÷y=(2x-120)*100÷(x-100)÷y
(x+120)(x-100)=(2x-120)*100
x^2-180x=0
x(x-180)=0
x=180
设A、B相距x米,A的速度为y,
B的速度为(x-100)÷(100/y)=y(100-x)/100
(x+120)÷y=(2x-120)*100÷(x-100)÷y
(x+120)(x-100)=(2x-120)*100
x^2-180x=0
x(x-180)=0
x=180