Question

公式法解方程x²-5x+2=0

x²=6x+1
2x²-3x=0
3x²+6x-5=0
0.2x²-0.1=0.4x
√2 x-2=2x²
求过程～我会加悬赏的

Answer 1

x²-5x+2=0
x²-5x+25/4=25/4-2
(x-5/2)²=17/4
x-5/2=±(√17)/2
x=(5±√17)/2

x²=6x+1
x²-6x+9=1+9
(x-3)²=10
x-3=±√10
x=3±√10

2x²-3x=0
x²-3x/2+9/16=9/16
(x-3/4)²=9/16
x-3/4=±3/4
∴x1=0
x2=3/2

3x²+6x+5=0
△=36-4*3*5=36-60＜0
∴原方程无解

0.2x²-0.1=0.4x
2x²-4x-1=0
x²-2x=1/2
x²-2x+1=1/2+1
(x-1)²=3/2
x-1=±√(3/2)
x=1±1/2√6

√2x-2=2x²
2x²-√2x+2=0
△=(√2)²-4*2*2=2-16＜0
∴原方程无解

Answer 2