1. ${\displaystyle \frac{f(x+h)-f(x)}{h}}=2x+h-3$

3. $f^{-1}(x)={\displaystyle \frac{1}{2}}x+{\displaystyle \frac{3}{2}}f(f^{-1}(x))=f\left({\displaystyle \frac{1}{2}}x+{\displaystyle \frac{3}{2}}\right)=2\left({\displaystyle \frac{1}{2}}x+{\displaystyle \frac{3}{2}}\right)-3=x+3-3=x$

5. $x=4$

7. $(2,\infty )$

9. $x=2,y=3$

11. $x=2,y=2-\text{ log }2$

13. 0

15. $A^{-1}=\left[\begin{array}{ll}2\hfill & 1\hfill \\ {\displaystyle \frac{5}{2}}\hfill & {\displaystyle \frac{3}{2}}\hfill \end{array}\right]$

17. $1,-1,{\displaystyle \frac{1}{2}}\sqrt{6},-{\displaystyle \frac{1}{2}}\sqrt{6}$

19. Circle