2x^2-4x-5=02x^2-4x+2=72(x-1)^2=7(x-1)^2=7/2x-1=√14/2或x-1=-√14/2x1=1+√14/2,x2=1-√14/2
2x^2-4x-5=0x^2-2x+1=3.5(x-1)^2=3.5x-1=土√3.5x1=1+ √3.5 x2=1-√3.5
