Question

（x-2分之1y-1)(x-2分之1y+1)-（x-2分之1y-1)^2,其中,x=1.5 y=3.9

Answer 1

[x-(y-1)/2][x-(y+1)/2]-[x-(y-1)/2]^2

=[x-(y-1)/2][x-(y+1)/2-x+(y-1)/2]

=[x-(y-1)/2](y-1-y-1)/2

=-[x-(y-1)/2]

将x=1.5 y=3.9带入上式可得

=-0.05