Question

用配方法解方程：2x2－X－1=0？

Answer 1

2x^2 -x-1=0
2[x^2 -2*x*(1/衫兆氏4)+(1/4)^2] -1-(1/8)=0
2[x-(2/或散4)]^2 = 9/8
[x-(1/4)]^2 =9/16
x-(1/4) = 正负猜液3/4
x1=1，x2= -1/2

Answer 2

2(x^2-x/2)=1，2[(x-1/4)^2-1/16]=1，[(x-1/4)^2-1/16]=1/2，掘察并判迹(x-1/4)^2=9/16，x-1/没神4=±3/4。