先化简,在求值; (2m-m^2n)/(m^2n^2-4),其中m=2,n=-3

问题描述:

先化简,在求值; (2m-m^2n)/(m^2n^2-4),其中m=2,n=-3

(2m-m^2n)/(m^2n^2-4).
=[m(2-mn)]/[(mn+2)(mn-2)]
=-m/(mn+2)
=-2/(-4)
=1/2