(3+x+5)(3+x-5)=0

(x+8)(x-2)=0

x 1=-8，x2=2

7+23x-20x^2=0

20x^2-23x-7=0

(5x-7)(4x+ 1)=0

x 1=7/5，x2=- 1/4

3-x^2=-2x

x^2-2x-3=0

(x-3)(x+ 1)=0

x 1=3，x2=- 1

19x+ 10= 10x+x^2

x^2-9x- 10=0

(x- 10)(x+ 1)=0

x 1= 10，x2=- 1

5x- 18=2(x-50)

5x- 18=2x- 100

3x=-82

x=-82/3

3x- 1 1-(x-3)^2=0

3x- 1 1-x^2+6x-9=0

x^2-9x+20=0

(x-4)(x-5)=0

x 1=4，x2=5