9.

1. No

2. Yes

11.

1. Yes

2. No

13.

1. Yes

2. Yes

15. $(-\infty ,-2)\cup (-2,1)\cup (1,\infty )$

17. $(-\infty ,3)\cup (3,4)\cup (4,\infty )$

19. No, $x=0$

21. Yes

23. $\{3\}$

25. $\{-2\}$

27. $\{7\}$

29. $\{-1\}$

31. $\{6\}$

33. $\{12\}$

35. $\{1\}$

37. $\{-11\}$

39. $\left\{{\displaystyle \frac{23}{6}}\right\}$

41. $\left\{{\displaystyle \frac{7}{8}}\right\}$

43. $\{2\}$

45. $\{28\}$

47. $\left\{{\displaystyle \frac{4}{5}}\right\}$

49. $r={\displaystyle \frac{d}{t}}$

51. $r={\displaystyle \frac{C}{2\pi }}$

53. $R={\displaystyle \frac{E}{I}}$

55. $h={\displaystyle \frac{2A}{a+b}}$

57. $u={\displaystyle \frac{fv}{v-f}}$

59. $m={\displaystyle \frac{y-b}{x}}$