问题:

先化简,再求值:(3m-4n)^2+2(3m-4n)(3m+4n)-3(3m+4n)^2,其中m=-2,n=1∕4

更新时间:2024-03-28 22:01:20

问题描述:

先化简,再求值:(3m-4n)^2+2(3m-4n)(3m+4n)-3(3m+4n)^2,其中m=-2,n=1∕4

宫殿荣回答:

  (3m-4n)^2+2(3m-4n)(3m+4n)-3(3m+4n)^2

  =9m^2-24mn+16n^3+18m^2-32n^2-27m^2-72mn-48n^2

  =-96mn-64n^2

  =-96*(-2)*1/4-64*(1/4)^2

  =48-4

  =44