设m-n=4分之1,m+n=2,求求[m^2+2mn+n^2分之m^2+n^2-mn分之2÷(m分之1+n分之1)^2]×m-n分之1
问题描述:
设m-n=4分之1,m+n=2,求求[m^2+2mn+n^2分之m^2+n^2-mn分之2÷(m分之1+n分之1)^2]×m-n分之1
答
[(m^2+n^2)/(m+n)^2-(2/mn)/(1/m+1/n)^2]*1/(m-n)
=[(m^2+n^2)/(m+n)^2-(2/mn)*(mn)^2/(m+n)^2]/(m-n)
=[(m^2+n^2)/(m+n)^2-2mn/(m+n)^2]/(m-n)
=(m-n)^2/[(m+n)^2*(m-n)]
=(m-n)/(m+n)^2
m-n=1/4
m+n=2
=(1/4)/2^2
=1/16