Question

解方程 x²-3x+4=0 2x²+x-1=0 x²+x-1=0

Answer 1

x²-3x+4=0

（x-3/2)^2=-4+9/4=-1.75

在实数范围内无解

2. 2x²+x-1=0

x^2+x/2=1/2

(x+1/4)^2=9/16

x+1/4=土3/4

x1=1/2 x2=-1

3. x²+x-1=0

(x+1/2)^2=5/4

x+1/2=±√5/2

x1=-1/2+√5/2 x2=-1/2-√5/2 .