解方程 3x²-x-2=0 4x²-2x-1=0rt 3x²-x-2=0 4x²-2x-1=0 2x²-3x-3=0 4x²-x-1=0 2y²+5y+1=0 3x²+5=9x

分类: 作业答案 • 2021-12-19 10:56:06

问题描述：

解方程 3x²-x-2=0 4x²-2x-1=0
rt 3x²-x-2=0 4x²-2x-1=0 2x²-3x-3=0 4x²-x-1=0 2y²+5y+1=0 3x²+5=9x

答

2. 4x²-2x-1=0

x^2-x/2=1/4

(x-1/4)^2=5/16

x-1/4=±√5/4

x1=1/4+√5/4 x2=1/4-√ 5/4

3. 2x²-3x-3=0

x^2-3x/2=3/2

(x-3/4)^2=3/2+9/16=33/16

x-3/4=±√33/4

x1=3/4+√33/4 x2=3/4-√ 33/4

4. 4x²-x-1=0

x^2-x/4=1/4

(x-1/8)^2=1/4+1/64=17/64

x-1/8=±√17/8

x1=1/8+√17/8 x2=1/8-√17/8

5. 2y²+5y+1=0

y^2+5y/2=-1/2

(y+5/4)^2=-1/2+25/16=17/16

y+5/4=±√17/4

y1=-5/4+√17/4 y2=-5/4-√17/4 .

6. 3x²+5=9x

x^2-3x=-5/3

(x-3/2)^2=-5/3+9/4=7/12

x-3/2=±√(7/12)

x1=3/2+√21/6 x2=3/2-√21/6

答

答

1、3x²-x-2=0 （3x+2）（x-1）=0 x=-2／3,x=12、4x²-2x-1=0配方法：x²-1/2x-1/4=0x²-1/2x+1/16-1/16-1/4=0(x-1/4)²-5/16=0(x-1/4)²=5/16x-1/4=±√5/4x=(1±√5)/43、 2x²-3x...