1.4x^2-4x-3=0 2 1 (2x+1)(2x-3)=02 -3因此x1=-1/2 x2=3/22.x=（-6+ -根号（6^2-4*3*(-5)))/2*3 x1=-1+2根号6/3 x2=-1-2根号6/33.x=(1+ -根号(1-4*4*(-9)))/2*4x1=1/8+根号145/8 x2=1/8-根号145/8