In inline equations, should I use parentheses to represent the sum of two or more variables?
Let me give an example.
Suppose that there are $5$ nodes, denoted by $n_1, n_2, \ldots, n_5$, and each node has its own reward value according to its given weight. We denote the reward value of node $i$ when its weight is $x_i$ by $f_i(x_i)$.
In this case, which of the following two sentences is better?
The problem considered in this paper is the optimization problem with the goal of maximizing the sum reward with weight $x_i + y_i$ for node $i$.
The problem considered in this paper is the optimization problem with the goal of maximizing the sum reward with weight $(x_i + y_i)$ for node $i$.