x^4+y^4=50 x^2y-xy^2=-14 求代数式x^4- y^4+3xy^2-xy^2-5x^2y+3x^2y-2y^4的值
问题描述：
x^4+y^4=50 x^2y-xy^2=-14 求代数式x^4- y^4+3xy^2-xy^2-5x^2y+3x^2y-2y^4的值
答
题有错吧.因该是+2y^4吧
x^4- y^4+3xy^2-xy^2-5x^2y+3x^2y+2y^4
=x^4+ y^4+2xy^2-2x^2y
=50-2*(-14)
=78