3x^2-5x-2=0 配方法

Question

如题所述

Answer 1

3x^2-5x-2=0
x²-5x/3=2/3
x²-5x/3+(5/6)²=2/3+25/36
(x-5/6)²=49/36
x-5/9=±7/6
x=5/9+7/6或x=5/9-7/6
即：x=31/18或x=-11/18

Answer 2

⑴2x²+5x-3=0
（2x-1)(x+3)=0
2x-1=0 x=1/2
x+3=0 x=-3
⑵5x+2=3x²
3x²-5x-2=0
x1=(-(-5)+√((-5)²-4×3×(-2)))÷(2×3)=2
x2=(5-7)/6=-1/3
⑶2x(x-3)=5(x-3)
2x²-6x=5x-15
2x²-11x+15=0
(2x-5)(x-3)=0
2x-5=0 x=5/2
x-3=0 x=3
⑷(2x+3)(x-2)=4
2x²-4x+3x-6-4=0
2x²-x-10=0
(2x-5)(x-3)=0
2x-5=0 x=5/2
x-3=0 x=3本回答被提问者采纳