杭州交通信息网教师党员年度自我评价:初一数学
来源：百度文库 编辑：杭州交通信息网 时间：2024/04/30 01:46:12
已知m^2-mn=21,mn-n^2=-12,求代数式m^2-n^2与2mn+n^2的值
(要过程)
(要过程)
m^2-mn+(mn-n^2)=m^2-n^2=21-12=9
mn=n^2-12 m=(n^2-12)/n m^2=(n^4-24n^2+144)/n^2
m^2-n^2=(144-24n^2)/n^2=9
n^2=144/33 2mn+n^2=3n^2-24=-120/11
m^2-mn+(mn-n^2)=m^2-n^2=21-12=9
mn=n^2-12 m=(n^2-12)/n m^2=(n^4-24n^2+144)/n^2
m^2-n^2=(144-24n^2)/n^2=9
n^2=144/33 2mn+n^2=3n^2-24=-120/11
ok
m^2-mn+(mn-n^2)=m^2-n^2=21-12=9
mn=n^2-12 m=(n^2-12)/n m^2=(n^4-24n^2+144)/n^2
m^2-n^2=(144-24n^2)/n^2=9
n^2=144/33 2mn+n^2=3n^2-24=-120/11
ok