1200/x-1200/（x+2）=30
问题描述：
1200/x-1200/（x+2）=30
答
1200/x-1200/（x+2）=30
40(x+2)-40x=x(x+2)
40x+80-40x=x²+2x
x²+2x-80=0
(x+10)(x-8)=0
x1=-10,x2=8