令a=1+2/3*(7/3)^1/2,b=1-2/3*(7/3)^1/2a²+b³=2ab=-1/3则(a+b)³=a³+b³+3ab(a+b)=2-(a+b)令x=a+bx³-1+x-1=0(x-1)(x²+x+1)+(x-1)=0(x-1)(x²+x+2)=0x=1所以原式=a+b=x=1
