先化简,再求值:(m+2)/(m²-2m)-(m-1)/(m²-4m+4)÷(m-1)/(m),其中m=4

问题描述:

先化简,再求值:(m+2)/(m&sup2-2m)-(m-1)/(m&sup2-4m+4)÷(m-1)/(m),其中m=4

原式=(m+2)/m(m-2)-(m-1)/(m-2)²×m/(m-1)
=(m+2)/m(m-2)-m/(m-2)²
=[(m+2)(m-2)-m²]/m(m-2)²
=-4/[m(m-2)²]