解下列方程: (1)(4x+3)(5-x)=0 (2)(x-1)^2+2x(x-1)=0 (3)2x^2-4x-5=0

2024-11-25 22:48:48
推荐回答(1个)
回答(1):

(1)(4x+3)(5-x)=0
x=-3/4 x=5
(2)(x-1)^2+2x(x-1)=0
(x-1)(x-1+2x)=0
x=1 x=1/3
(3)2x^2-4x-5=0
x=4+√16+4*2*5/2*2=4+√56/4=2+√14/2
或x=4-√16+4*2*5/2*2=4-√56/4=2-√14/2

(4)-3x^2-4x-5=0
判别式=16-4*3*5<0
方程无解

(5)3x(x-1)=2-2x
3x^2-3x=2-2x
3x^2-x-2=0
(3x+2)(x-1)=0
x=-2/3 x=1

(6)(x-1)(x+2)=70
x^2+x-2=70
x^2+x-72=0
(x-8)(x+9)=0
x=8 x=-9
(7)x(x+6)=7
x^2+6x-7=0
(x-1)(x+7)=0
x=1 x-7
(8)(3-x)^2+x^2=9
9-6x+x^2+x^2=9
x^2-3x=0
x(x-3)=0
x=0 x=3