2/(2x-1)=4/(4x^2-1)
两边同乘4x^2-1
2(2x+1)=4
4x+2=4
4x=2
x=1/2
(2)
(2x+1)/(x^2+x)=5/(6x+6)
两边同乘6x(x+1)
6(2x+1)=5x
12x+6=5x
7x=-6
x=-6/7