1.x+y=a,xy=b 求X2次方+y2次方 x3次方+y3次方 x4次方+y4次方 x5次方+y5次方

X^2+y^2=(x+y)^2-2Xy=a^2-2bx3次方+y3次方=(x+y)(X^2+y^2-xy)=a(a^2-2b-b)=a^3-3abx4次方+y4次方=(x^2+y^2)^2-2x^2y^2=(a^2-2b)^2-2b^2=a^4-4a^2b+2b^2x5次方+y5次方=(x^4+y^4)(x+y)-xy(x^3+y^3)将以上知道的代入这...