已知m^2-mn=7,mn-n^2=-2,求m^2-n^2及m^2-2mn+n^2的值._数学解答

已知m^2-mn=7,mn-n^2=-2,求m^2-n^2及m^2-2mn+n^2的值.

人气：301 ℃　时间：2020-03-26 08:29:24

解答

m^2-mn=7,mn-n^2=-2,
相加
m^2-mn+mn-n^2=7-2
m^2-n^2=5
相减
m^2-mn-mn+n^2=7+2
m^2-2mn+n^2=9