x+y=3,xy=1则(x+y)²=9x²+y²=9-2xy=7x³+y³=(x+y)(x²-xy+y²)=3[(x+y)²-3xy]=3×(9-3)=18x的五次方+y的五次方=(x²+y²)(x³+y³)-x²y³-x³y&s...