4x2-6x-3=0(2x)²-2*2x*3/2+9/4=9/4+3(2x-3/2)²=21/42x-3/2=±√21/22x=3/2±√21/2x=3/4+√21/4或x=3/4-√21/4
4x2-6x-3=0;4x²-6x+9/4-3-9/4=0;(2x-3/2)²=21/4;2x-3/2=±√21/2;2x=(±√21+3)/2;x=(±√21+3)/4
即(2X-3)(2X+1)=0X=3/2或X=-1/2
222lou