1. $\begin{array}[t]{ccc} (x)^2&-&(8)^2 \\ x^2&-&64 \end{array}$
2. $\begin{array}[t]{ccc} (a)^2&-&(4)^2 \\ a^2&-&16 \end{array}$
3. $\begin{array}[t]{ccc} (1)^2&-&(3p)^2 \\ 1&-&9p^2 \end{array}$
4. $\begin{array}[t]{ccc} (x)^2&-&(3)^2 \\ x^2&-&9 \end{array}$
5. $\begin{array}[t]{ccc} (1)^2&-&(7n)^2 \\ 1&-&49n^2 \end{array}$
6. $\begin{array}[t]{ccc} (8m)^2&-&(5)^2 \\ 64m^2&-&25 \end{array}$
7. $\begin{array}[t]{ccc} (4y)^2&-&(x)^2 \\ 16y^2&-&x^2 \end{array}$
8. $\begin{array}[t]{ccc} (7a)^2&-&(7b)^2 \\ 49a^2&-&49b^2 \end{array}$
9. $\begin{array}[t]{ccc} (4m)^2&-&(8n)^2 \\ 16m^2&-&64n^2 \end{array}$
10. $\begin{array}[t]{ccc} (3y)^2&-&(3x)^2 \\ 9y^2&-&9x^2 \end{array}$
11. $\begin{array}[t]{ccc} (6x)^2&-&(2y)^2 \\ 36x^2&-&4y^2 \end{array}$
12. $\begin{array}[t]{ccccc} (1)^2&+&2(1)(5n)&+&(5n)^2 \\ 1&+&10n&+&25n^2 \end{array}$
13. $a^2+10a+25$
14. $x^2-16x+64$
15. $1-12n+36n^2$
16. $16x^2-40x+25$
17. $25m^2-80m+64$
18. $9a^2+18ab+9b^2$
19. $25x^2+70xy+49y^2$
20. $16m^2-8mn+n^2$
21. $25+20r+4r^2$
22. $m^2-14m+49$
23. $16v^2-49$
24. $b^2-16$