This is LaTeX code:
[latex]
x^{i+1} \sum_{j=0}^{n-1} (a_{i-1} - b_j) x^j = x^{i+1} \sum_{j=0}^{n-1} (a_{i-1}) - x^{i+1} \sum_{j=0}^{n-1} (b_j) x^j
[/latex]