Question

1.M四次方+4n四次方=2.若x+y+z=5,xy+yz+xz=12,则(x+y)(y+z)(z+x)+xyz=3.计

Answer 1

1.m^4+4n^4=(m^2+2n^2)^2-4m^2n^2=(m^2+2n^2)^2-(2mn)^2=(m^2+2n^2-2mn)(m^2+2n^2+2mn)2.(x+y)(y+z)(z+x)+xyz=(5-z)(5-x)(5-y)+xyz=125-25y-25x+5xy-25z+5yz+5xz-xyz+xyz=125-25(x+y+z)+5(xy+yz+xz)=125-25*5+5*12=6...