The table is
\ \
x \ | \
\
y \ | \
\
1 \ | \
\
9 \ | \
\
2 \ | \
\
11 \ \ \ | \
\
3 \ | \
\
14 \ | \
\
4 \ | \
\
18 \ | \
From the table x increases by 1, y increases by a greater amount each time.
\So, this is a nonlinear function.
It represents a nonlinear function.