Question

1.已知：1/X-1/Y=3.则（2X-14XY-2Y）/（X-2XY-Y）的值.2,已知M-1/M=-1,求M^2+M

Answer 1

1,因为1/X-1/Y=3

所以X-Y=-3XY

所以(2X-14XY-2Y)/(X-2XY-Y)

=[2(X-Y)-14XY]/(X-Y-2XY)

=(-20XY)/(-5XY)

=4

2,因为M-1/M=-1

所以M^2+M-1=0

所以M^2+M=1

2M^2+2M+1=2(M^2+M)+1=3