I don’t know how to do this.

Answer:
[tex]a_{n} = \frac{n}{(n +1)^{2}}[/tex]
Step-by-step explanation:
[tex]a_{n} = \frac{n}{(n +1)^{2}}[/tex]
[tex]a_{1} = \frac{1}{(1 +1)^{2}} = \frac{1}{2^{2}} = \frac{1}{4}\\\\a_{2} = \frac{2}{(1 +2)^{2}} = \frac{2}{3^{2}} = \frac{2}{9}\\\\a_{3} = \frac{3}{(1 +3)^{2}} = \frac{3}{4^{2}} = \frac{3}{16}\\[/tex]