1)5x(x-4)-x(3+5x)=4

5x² - 20x - 3x - 5x² = 4

-23x = 4

x = -4/23

2)7x-2x²+4=x(5-2x)

7x - 2x² + 4 = 5x - 2x²

7x + 4 = 5x

7x - 5x = -4

2x = -4

x = -2

3)2x(3x-2)-3( x²-4 x)=3 x( x-7)+2

6x² - 4x - 3x² + 12x = 3x² - 21x + 2

3x² + 8x = 3x² - 21x + 2

8x = -21x + 2

8x + 21x = 2

30x = 2

x = 2/30 = 1/15

4) 4(2 - x²) - 3x(x - 3)=8+9x-7 x²

8 - 4x²- 3x² + 9x = 8 + 9x - 7x²

8 + 9x - 7x² = 8 + 9x - 7x²

0 = 0 => бесконечное множество решений