(3+2m-㎡)/㎡-7m+12,其中m=-1/2

问题描述:

(3+2m-㎡)/㎡-7m+12,其中m=-1/2

(3+2m-m^2)/(m^2-7m+12)
=-(m^2-2m-3)/(m^2-7m+12)
=-(m-3)(m+1)/[(m-3)(m-4)]
=-(m+1)/(m-4)
=-(-1/2+1)/(-1/2-4)
=1/9