(一)251^2-502+1
=251^2-2*251+1
=(251-1)^2
=250^2
=62500
(二)已知x+y=3,xy=2,求(x-2)(y-2)的值
(x-2)(y-2)
=xy-2x-2y+4
=xy-2(x+y)+4
=2-2*3+4
=0
(一)251^2-502+1
=251^2-2*251+1
=(251-1)^2
=250^2
=62500
(二)已知x+y=3,xy=2,求(x-2)(y-2)的值
(x-2)(y-2)
=xy-2x-2y+4
=xy-2(x+y)+4
=2-2*3+4
=0