x²+3x-1=0同时除以x,得:x+3-1/x=0x-1/x=3平方,得:x²-2+1/x²=9x²+1/x²=11
X-1/X=(5±2*13^0.5）÷2X^2+1/X^2=(41±3*13^0.5)/34
