The heights of the tree form an arithmetic sequence. The first measurement is 200 cm, so the first term a₁=200. The tree grows 0.5 cm per week, so the common difference d=0.5.
[tex]a_n=a_1+d(n-1) \\
a_n=200+0.5(n-1) \\
a_n=200+0.5n-0.5 \\
a_n=0.5n+199.5[/tex]
The equation for the weekly height is:
[tex]\boxed{a_n=0.5n+199.5}[/tex]
where n is the number of week.
