3X²-2X-4=0
X1+X2=2/3
X1X2=-4/3
根是1/x1,1/x2
1/x1+1/x2=(x1+x2)/(x1x2)=-1/2
1/x1*1/x2=1/(x1x2)=-3/4
所以x²+x/2-3/4=0
即4x²+2x-3=0