SOLUTION
9.
[tex]\begin{gathered} (x+10)^2\text{ = ( x + 10 ) ( x + 10 )} \\ =x^2\text{ + 10 x + 10x + 100} \\ =x^2\text{ + 20 x + 100} \end{gathered}[/tex]10.
[tex]\begin{gathered} (x-10)^2\text{ = ( x - 10 ) ( x - 10 )} \\ =x^2\text{ -10 x - 10 x + 100} \\ =x^2\text{ - 20 x + 100} \end{gathered}[/tex]11. ( x + 10 ) ( x - 10 ) ( Difference of two squares)
[tex]\begin{gathered} x^2\text{ - 10 x + 10 x - 100} \\ =x^2\text{ - 100} \end{gathered}[/tex]