2x²-5x-4=0 用配方解!谢谢各位大神啦!2x²-5x-4=0

2x²-5x-4=0 用配方解!谢谢各位大神啦!2x²-5x-4=0
2x²-5x-4=0 用配方解!谢谢各位大神啦!
2x²-5x-4=0

2x²-5x-4=0 用配方解!谢谢各位大神啦!2x²-5x-4=0
2x²-5x-4=0
x²-5x/2-2=0
x²-5x/2+(5/4)²=2+25/16
(x-5/4)²=57/16
x-5/4=±√(57/16)
x=5/4±√57/4
x1=(5+√57)/4 x2=(5-√57)/4