a,b是方程x²-3x+1=0的根所以有a²-3a+1=0a²-2a=a-1且由韦达定理知a+b=3a²-2a+b=(a-1)+b=(a+b)-1=3-1=2
解：由已经得：α~2 - 3α +1 =0,故α~2 - 2α = -1 +α；又根据韦达定理得：α+β = 3；故α~2 - 2α +β = -1 +α +β =-1 + 3 = 2
