解
(m+2)/(4m-3)=-1
m+2=-4m+3
5m=1
m=1/5
(2m-1)/(m²-3m-4)
=(2×1/5-1)/(1/25-3/5-4)
=(-3/5)/(-114/25)
=-3/5×(-25/114)
=15/114