原式=(2x+y)/(5xy-6xy)×(1/2)(x+2y)
=(x+y)/(-xy)×(1/2)(x+y)
=(-xy)/(2x+2y)
=(-xy)/2(x+y)
=(1/2)×(-xy)/(x+y)
当(xy)/(x+y)=4时,
原式=(1/2)×(-4)
=-2
原式=(2x+y)/(5xy-6xy)×(1/2)(x+2y)
=(x+y)/(-xy)×(1/2)(x+y)
=(-xy)/(2x+2y)
=(-xy)/2(x+y)
=(1/2)×(-xy)/(x+y)
当(xy)/(x+y)=4时,
原式=(1/2)×(-4)
=-2