Bonjour je ne comprends pas merci

bonjour

4 x - 5 = 9 x + 4

4 x - 9 x = 4 + 5

- 5 x = 9

x = - 9/5

x² + 3 - x = x² + 10 x - 7

x² - x² - x - 10 x = - 7 - 3

- 11 x = - 10

x = 10/11

1/2 + 4 x = 5 - 6 x /7

7/14 + 56 x/14 = 70/14 - 12 x /14

56 x + 12 x = 70 - 7

68 x = 63

x = 63/68

5 x = 5 x - 10 + 3

5 x - 5 x = - 7

0 x = - 7

comprends pas la f x ⁺ ?